Make non-static functions, that may be static, static

Signed-off-by: Stephan Beyer <s-beyer@gmx.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin-config.c b/builtin-config.c
index 0cf191a..91fdc49 100644
--- a/builtin-config.c
+++ b/builtin-config.c
@@ -145,7 +145,7 @@
 	return ret;
 }
 
-char *normalize_value(const char *key, const char *value)
+static char *normalize_value(const char *key, const char *value)
 {
 	char *normalized;