tmac: introduce real manual reference macro instead of overloading IR

The overloading of IR emits magic \X'...' sequences that turn into HTML manual links.
But not all such IR invocations should be manual links;
those had to be written to avoid the IR macro before.
Worse, the \X'...' ending the IR causes troff to emit only a single space after a period.

Defining a new IM macro for manual references fixes both problems.

Fixes #441.

man/man1/page.1

@@ -1,7 +1,7 @@
 .TH PAGE 1
 .SH NAME
-page \- view 
-FAX, 
+page \- view
+FAX,
 image, graphic, PostScript, PDF, and
 typesetter output
 files
@@ -24,23 +24,24 @@ It can be used to display the individual pages
 of a
 PostScript,
 PDF,
-or 
-.IR troff (1)
-or 
-Unix's \fItex\fR(1)
+or
+.IM troff (1)
+or
+Unix's
+.IR tex (1)
 device-independent output
 file.
 .I Troff
-or 
+or
 .I tex
 output is simply converted to PostScript in order to be viewed.
 It can also be used to view any number of
 graphics files
-(such as a 
+(such as a
 FAX
-page, 
+page,
 a Plan 9
-.IR image (7)
+.IM image (7)
 file, an Inferno bitmap file, or other common format).
 .I Page
 displays these
@@ -53,26 +54,26 @@ By default,
 .I page
 runs in the window in which it is started
 and leaves the window unchanged.
-The 
+The
 .B -R
-option causes 
-.I page 
+option causes
+.I page
 to grow the window if necessary
 to display the page being viewed.
 The
 .B -w
-option causes 
-.I page 
+option causes
+.I page
 to create a new window for itself.
 The newly created window will grow as under the
 .B -R
 option.
-If being used to display 
+If being used to display
 multipage documents,
 only one file may be specified on the command line.
 .PP
-The 
-.B -p 
+The
+.B -p
 option sets the resolution for PostScript and PDF
 files, in pixels per inch.
 The default is 100 ppi.
@@ -85,13 +86,13 @@ When viewing a document,
 will try to guess the true bounding box, usually rounding up from
 the file's bounding box to
 8½×11 or A4 size.
-The 
+The
 .B -b
 option causes it to respect the bounding box given in the file.
 As a more general problem,
 some PostScript files claim to conform to Adobe's
 Document Structuring Conventions but do not.
-The 
+The
 .B -P
 option enables a slightly slower and slightly more
 skeptical version of the PostScript processing code.
@@ -101,34 +102,35 @@ that can only be viewed with the
 option, and there are PostScript documents that
 can only be viewed without it.
 .PP
-When viewing images with 
+When viewing images with
 .IR page ,
-it listens to the 
+it listens to the
 .B image
 plumbing channel
-(see 
-.IR plumber (4))
+(see
+.IM plumber (4) )
 for more images to display.
-The 
+The
 .B -i
-option causes 
+option causes
 .I page
-to not load any graphics files nor to read 
+to not load any graphics files nor to read
 from standard input but rather to listen
 for ones to load from the plumbing channel.
 .PP
-The 
+The
 .B -v
 option turns on extra debugging output, and
 the
 .B -V
 option turns on even more debugging output.
-The 
+The
 .B -a
-option causes 
+option causes
 .I page
 to call
-Unix's \fIabort\fR(3)
+Unix's
+.IR abort (3)
 rather than exit cleanly on errors,
 to facilitate debugging.
 .PP
@@ -145,7 +147,7 @@ The button 2 menu operations are:
 Restores the image to the original. All modifications are lost.
 .TP
 .B Zoom
-Prompts the user to sweep a rectangle on the image which is 
+Prompts the user to sweep a rectangle on the image which is
 expanded proportionally to the rectangle.
 .TP
 .B Fit window
@@ -164,7 +166,7 @@ Displays the next page.
 Displays the previous page.
 .TP
 .B Zerox
-Displays the current image in a new page window. 
+Displays the current image in a new page window.
 Useful for selecting important pages from large documents.
 .TP
 .B Reverse
@@ -189,14 +191,14 @@ toggles whether images are displayed upside-down.
 Typing a
 .B r
 reverses the order in which pages are displayed.
-Typing a 
+Typing a
 .B w
 will write the currently viewed page to a new file as a compressed
-.IR image (7)
+.IM image (7)
 file.
 When possible, the filename is of the form
 .IR basename . pagenum . bit .
-Typing a 
+Typing a
 .B d
 removes an image from the working set.
 .PP
@@ -208,13 +210,14 @@ changing pages when panning off the top or bottom of the page.
 .PP
 .I Page
 calls
-Unix's \fIgs\fR(1)
+Unix's
+.IR gs (1)
 to draw each page of PostScript
 and
 PDF
 .IR files .
 It also calls a variety of conversion programs, such as those described in
-.IR jpg (1),
+.IM jpg (1) ,
 to convert the various raster graphics formats
 into Inferno bitmap files.
 Pages are converted ``on the fly,'' as needed.
@@ -232,11 +235,11 @@ Browse the Inferno bitmap library.
 man -t page | page -w
 Preview this manual in a new window.
 .SH "SEE ALSO
-.IR gs (1),
-.IR jpg (1),
-.IR proof (1),
-.IR tex (1),
-.IR troff (1)
+.IM gs (1) ,
+.IM jpg (1) ,
+.IM proof (1) ,
+.IM tex (1) ,
+.IM troff (1)
 .SH SOURCE
 .B \*9/src/cmd/page
 .SH DIAGNOSTICS
@@ -254,19 +257,19 @@ When viewing multipage PostScript files that do not contain
 .RB `` %%Page ''
 comments, the button 3 menu only contains
 ``this page'' and ``next page'':
-correctly determining 
+correctly determining
 page boundaries in Postscript code is not computable
 in the general case.
 .PP
 If
 .I page
 has trouble viewing a Postscript file,
-it might not be exactly conforming: try viewing it with the 
+it might not be exactly conforming: try viewing it with the
 .B -P
 option.
 .PP
 The interface to the plumber is unsatisfactory.  In particular,
-document references cannot be sent 
+document references cannot be sent
 via plumbing messages.
 .PP
 There are too many keyboard commands and menu items.
@@ -274,7 +277,7 @@ There are too many keyboard commands and menu items.
 Displaying a PostScript or PDF file depends both on having
 GhostScript
 (see
-.IR gs (1))
+.IM gs (1) )
 installed and on the underlying operating system
 providing a file descriptor device tree at
 .BR /dev/fd .