Add command line option to suppress dialogs

Implement a -q/--quiet command line option to disable system dialogs
temporarily.

Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>

src/utils.c

@@ -1653,3 +1653,8 @@ int hash_matches(const char *pattern, const char *hash)
 
 	return (starts_with(hash, pattern) != invert);
 }
+
+int show_dialogs(void)
+{
+	return (!quiet) && conf.system_dialogs;
+}