dep/libchdr: Add chd_precache_progress()

Alternative which reports back as the file is read.

dep/libchdr/include/libchdr/chd.h

@@ -375,6 +375,7 @@ CHD_EXPORT chd_error chd_open(const char *filename, int mode, chd_file *parent,
 
 /* precache underlying file */
 CHD_EXPORT chd_error chd_precache(chd_file *chd);
+CHD_EXPORT chd_error chd_precache_progress(chd_file* chd, void(*progress)(size_t pos, size_t total, void* param), void* param);
 
 /* close a CHD file */
 CHD_EXPORT void chd_close(chd_file *chd);