Number of fixes: don't hold mutex while loading, fix ui crash when kit index out of range, don't load negative kit indexes, respond to midi base note port events.

Most important here is that the mutex change means the run loop with not block for a significant period ever, which previously was causing the jack thread to get zombified.

drmr_hydrogen.h

@@ -22,6 +22,6 @@ kits* scan_kits();
 void free_kits(kits* kits);
 void free_samples(drmr_sample* samples, int num_samples);
 int load_sample(char* path,drmr_layer* layer,double target_rate);
-int load_hydrogen_kit(DrMr* drmr, char* path);
+drmr_sample *load_hydrogen_kit(char *path, double rate, int *num_samples);
 
 #endif // DRMR_HYDRO_H