PowerPC Linux support from ericvh.

Mainly adding va_copy/va_end.
Also fix bug in sprint wrapping
around top of memory.

src/mkhdr

@@ -1,5 +1,5 @@
 SYSNAME=`uname`
-OBJTYPE=`uname -m | sed 's;i.86;386;; s;/.*;;; s; ;;g'`
+OBJTYPE=`uname -m | sed 's;i.86;386;; s;/.*;;; s; ;;g' | sed 's/ppc64/power/g' | sed 's/ppc/power/g'`
 
 BIN=$PLAN9/bin
 LIBDIR=$PLAN9/lib