Git.xs: older perl do not know const char *

Both of these casts _should_ be safe, since you do not want to muck around
with the version or the path anyway.

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

perl/Git.xs

@@ -59,7 +59,7 @@ BOOT:
 # /* TODO: xs_call_gate(). See Git.pm. */
 
 
-const char *
+char *
 xs_version()
 CODE:
 {
@@ -69,11 +69,11 @@ OUTPUT:
 	RETVAL
 
 
-const char *
+char *
 xs_exec_path()
 CODE:
 {
-	RETVAL = git_exec_path();
+	RETVAL = (char *)git_exec_path();
 }
 OUTPUT:
 	RETVAL