Move the MAX macro to a util.h so it becomes usable in other modules.

Suggested by:	Max Okumoto <okumoto@ucsd.edu>

usr.bin/make/buf.c

@@ -55,10 +55,6 @@ __FBSDID("$FreeBSD$");
 #include "sprite.h"
 #include "util.h"
 
-#ifndef MAX
-#define	MAX(a,b)  ((a) > (b) ? (a) : (b))
-#endif
-
 /**
  * Returns the number of bytes in the buffer.  Doesn't include the
  * null-terminating byte.

usr.bin/make/util.h

@@ -85,6 +85,10 @@ do {						\
 #define	ISDOT(c) ((c)[0] == '.' && (((c)[1] == '\0') || ((c)[1] == '/')))
 #define	ISDOTDOT(c) ((c)[0] == '.' && ISDOT(&((c)[1])))
 
+#ifndef MAX
+#define	MAX(a, b)  ((a) > (b) ? (a) : (b))
+#endif
+
 void Debug(const char *, ...);
 void DebugM(const char *, ...);
 void Error(const char *, ...);