wcwidth redeclaration

Build fails for git 1.5.1.3 on AIX, with the message:

utf8.c:66: error: conflicting types for 'wcwidth'
/.../lib/gcc/powerpc-ibm-aix5.3.0.0/4.0.3/include/string.h:266: error: previous declaration of 'wcwidth' was here

Fix this by renaming our static variant to our own name.

Signed-off-by: Amos Waterland <apw@us.ibm.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

utf8.c

@@ -62,7 +62,7 @@ static int bisearch(ucs_char_t ucs, const struct interval *table, int max) {
  * in ISO 10646.
  */
 
-static int wcwidth(ucs_char_t ch)
+static int git_wcwidth(ucs_char_t ch)
 {
 	/*
 	 * Sorted list of non-overlapping intervals of non-spacing characters,
@@ -207,7 +207,7 @@ invalid:
 		return 0;
 	}
 
-	return wcwidth(ch);
+	return git_wcwidth(ch);
 }
 
 int is_utf8(const char *text)