Match file extensions case-insensitively when saving.

--- v1.4.24/src/filetypes.c	2017-09-21 17:07:16.000000000 +0100
+++ v1.4.24/src/filetypes.c	2025-06-15 00:18:26.802529592 +0100
@@ -22,6 +22,7 @@
 #include <config.h>
 
 #include <string.h>
+#include <strings.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <signal.h>
@@ -319,7 +320,7 @@
 	  ft = (struct file_type *)l->data;
 	  if (!ft->extension) continue;
 	  c = strchr(filename,0) - strlen(ft->extension);
-	  if (c<filename || strcmp(c,ft->extension)!=0) continue;
+	  if (c<filename || strcasecmp(c,ft->extension)!=0) continue;
 	  if (ft->save != NULL)
 	       return ft;
      }