Add a compat/strtoumax.c for Solaris 8.

Solaris 8 was pre-c99, and they weren't willing to commit to
the strtoumax definition according to /usr/include/inttypes.h.

This adds NO_STRTOUMAX and NO_STRTOULL for ancient systems.
If NO_STRTOUMAX is defined, the routine in compat/strtoumax.c
will be used instead.  That routine passes its arguments to
strtoull unless NO_STRTOULL is defined.  If NO_STRTOULL, then
the routine uses strtoul (unsigned long).

Signed-off-by: Jason Riedy <ejr@cs.berkeley.edu>
Acked-by: Shawn O Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/git-compat-util.h b/git-compat-util.h
index 105ac28..9863cf6 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -139,6 +139,11 @@
 extern size_t gitstrlcpy(char *, const char *, size_t);
 #endif
 
+#ifdef NO_STRTOUMAX
+#define strtoumax gitstrtoumax
+extern uintmax_t gitstrtoumax(const char *, char **, int);
+#endif
+
 extern void release_pack_memory(size_t);
 
 static inline char* xstrdup(const char *str)