Add system.git_date proprety (string)

src/sbbs3/js_system.c

@@ -633,6 +633,7 @@ static const char* sys_prop_desc[] = {
 	,"Synchronet version number in hexadecimal (e.g. 0x31301 for v3.13b)"
 	,"Synchronet Git repository branch name"
 	,"Synchronet Git repository commit hash"
+	,"Synchronet Git repository commit date/time"
 	,"Platform description (e.g. 'Win32', 'Linux', 'FreeBSD')"
 	,"Architecture description (e.g. 'i386', 'i686', 'x86_64')"
 	,"Message base library version information"
@@ -2692,6 +2693,7 @@ static JSBool js_system_resolve(JSContext *cx, JSObject *obj, jsid id)
 	/* Git repo details */
 	LAZY_STRING("git_branch", git_branch);
 	LAZY_STRING("git_hash", git_hash);
+	LAZY_STRING("git_date", git_date);
 
 	LAZY_STRING("platform", PLATFORM_DESC);
 	LAZY_STRING("architecture", ARCHITECTURE_DESC);