Make !INCLUDE directives filename case-insensitive

Some legacy Baja source files !INCLUDE SBBSDEFS.INC, but the filename is now
sbbsdefs.inc, which does not match on case-sensitive filesystems (e.g. Linux)
e.g.
BBSLISTR.ZIP:!INCLUDE SBBSDEFS.INC
FORSALE1.ZIP:!INCLUDE SBBSDEFS.INC
FWISH10.ZIP:!INCLUDE SBBSDEFS.INC
GUESS20.ZIP:!INCLUDE SBBSDEFS.INC
NU_SYNC.ZIP:!INCLUDE SBBSDEFS.INC
ONELINE1.ZIP:!INCLUDE SBBSDEFS.INC
ni-sbbs.zip:!INCLUDE SBBSDEFS.INC

This issue was reported via DOVE-Net by Rick Smith.

src/sbbs3/baja.c

-/* baja.c */
-
 /* Synchronet command shell/module compiler */
 
-/* $Id: baja.c,v 1.52 2020/05/14 07:49:59 rswindell Exp $ */
-
 /****************************************************************************
  * @format.tab-size 4		(Plain Text/Source Code File Header)			*
  * @format.use-tabs true	(see http://www.synchro.net/ptsc_hdr.html)		*
@@ -17,21 +13,9 @@
  * See the GNU General Public License for more details: gpl.txt or			*
  * http://www.fsf.org/copyleft/gpl.html										*
  *																			*
- * Anonymous FTP access to the most recent released source is available at	*
- * ftp://vert.synchro.net, ftp://cvs.synchro.net and ftp://ftp.synchro.net	*
- *																			*
- * Anonymous CVS access to the development source and modification history	*
- * is available at cvs.synchro.net:/cvsroot/sbbs, example:					*
- * cvs -d :pserver:anonymous@cvs.synchro.net:/cvsroot/sbbs login			*
- *     (just hit return, no password is necessary)							*
- * cvs -d :pserver:anonymous@cvs.synchro.net:/cvsroot/sbbs checkout src		*
- *																			*
  * For Synchronet coding style and modification guidelines, see				*
  * http://www.synchro.net/source.html										*
  *																			*
- * You are encouraged to submit any modifications (preferably in Unix diff	*
- * format) via e-mail to mods@synchro.net									*
- *																			*
  * Note: If this box doesn't appear square, then you need to fix your tabs.	*
  ****************************************************************************/
 
@@ -519,6 +503,7 @@ void compile(char *src)
 			sp=strchr(arg,' ');
 			if(sp) *sp=0;
 			sprintf(path,"%s%s",include_dir,arg);
+			fexistcase(path);
 			compile(path);
 			line=savline;
 			continue;