git-config-set: Properly terminate strings with '\0'

When a lowercase version of the key was generated, it was not
terminated. Strangely enough, it worked on Linux and macosx anyway.
Just cygwin barfed.

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

config-set.c

@@ -38,6 +38,7 @@ static int get_value(const char* key_, const char* regex_)
 	key = malloc(strlen(key_)+1);
 	for (i = 0; key_[i]; i++)
 		key[i] = tolower(key_[i]);
+	key[i] = 0;
 
 	if (regex_) {
 		if (regex_[0] == '!') {

config.c

@@ -432,6 +432,7 @@ int git_config_set_multivar(const char* key, const char* value,
 			return 1;
 		} else
 			store.key[i] = tolower(key[i]);
+	store.key[i] = 0;
 
 	/*
 	 * The lock_file serves a purpose in addition to locking: the new