add support for decoding Xtc's composed feature names

Xtc does not evaluate expressions in all cases and may return strings if
evaluation depends on specific values. Fixed by parsing those expressions again
updated the lexer tests and also test the Xtc lexer with the same files
add test to ensure the lexer uses MacroFilters correctly
Merge branch 'master' into xtc240
fix use of macrofilter in xtc again

(lost in merge)