define MAXPATHLEN for hosts that don't support it

[jc: Martin says syllable (www.syllable.org) wants this.]
Signed-off-by: NJunio C Hamano <junkio@cox.net>

git-compat-util.h

@@ -110,4 +110,7 @@ static inline int sane_case(int x, int high)
 	return x;
 }
 
+#ifndef MAXPATHLEN
+#define MAXPATHLEN 256
+#endif
 #endif