adapt to libfirm bitfield changes

Also fixes a bug where initializer for structs with anonymous bitfield
members had too many elements.
update libFirm to get sparc bugfix
fix asflags getting lost when assembling multiple files
update to get libfirm bitfield sel fix
add a workaround to avoid early construction of firm compound types

Otherwise we have cases like firm-testsuite/C/cp_error075.c where the
firm type is constructed before all members of the compound are known.