Enhance xlat generator

* xlat/gen.sh: Define all xlat structs not declared in defs.h as static.
Some symbolic constants are not macros, extend #ifdef check to cover
symbolic constants checked by AC_CHECK_DECLS.
Handle complex symbolic constants in SYMBOL|... form.
Handle symbolic constants in 1<<SYMBOL form.
Handle numeric constants.
Implement #unconditional directive that turns off preprocessor checks.
Implement #unterminated directive that turns off adding XLAT_END.
1 file changed