-fdollar-in-identifiers switch which enables '$' in identifiers

library Cello: http://libcello.org/ which uses `$` and several
    variations of as macros.

    There is also RayLanguage which also uses it as a macro for a kind of
    ObjC style message passing: https://github.com/kojiba/RayLanguage

    This is a patch from Daniel Holden.

tcc.h

@@ -605,6 +605,7 @@ struct TCCState {
     int ms_extensions;		/* allow nested named struct w/o identifier behave like unnamed */
     int old_struct_init_code;	/* use old algorithm to init array in struct when there is no '{' used.
 				   Liuux 2.4.26 can't find initrd when compiled with a new algorithm */
+    int dollars_in_identifiers;	/* allows '$' char in indentifiers */
     
     /* warning switches */
     int warn_write_strings;