Use XMP_MAX_SRATE for -f limit instead of 48000. (#74)

Preserve the old limit of 48000 if xmp_vercode indicates an older
library version.

Author: AliceLR

Changelog

@@ -7,6 +7,7 @@ Stable versions
 	  a default panning value (sub->pan < 0).
 	- Don't unmute muted IT channels unless explicitly unmuted by
 	  the -S/--solo option.
+	- Use XMP_MAX_SRATE as the limit for -f instead of 48000.
 
 4.2.0 (20230615):
 	Changes by Özkan Sezer:

src/options.c

@@ -382,8 +382,13 @@ void get_options(int argc, char **argv, struct options *options)
 	/* Set limits */
 	if (options->rate < 1000)
 		options->rate = 1000;	/* Min. rate 1 kHz */
-	if (options->rate > 48000)
-		options->rate = 48000;	/* Max. rate 48 kHz */
+	if (options->rate > XMP_MAX_SRATE)
+		options->rate = XMP_MAX_SRATE;	/* Max. rate 768 kHz */
+
+	if (xmp_vercode < 0x040700) {
+		if (options->rate > 48000)
+			options->rate = 48000;	/* Old max. rate 48kHz */
+	}
 
 	/* apply guess if no driver selected */
 	if (!options->driver_id)