Fix Savannah bug #19656: rationalize our use of case-insensitive string

comparison functions to always use POSIX strcasecmp().  For non-POSIX
systems that use other functions (strcmpi or stricmp) use a macro to alias
strcasecmp to those.  If we can't find any of them (VMS, plus whatever
UNIX doesn't have them) then define our own version in misc.c.

function.c

@@ -2274,7 +2274,7 @@ func_call (char *o, char **argv, const char *funcname UNUSED)
     {
       /* How many arguments do we have?  */
       for (i=0; argv[i+1]; ++i)
-  	;
+        ;
       return expand_builtin_function (o, i, argv+1, entry_p);
     }