Fix -split-obj on Mac OS via -fasm
The problem of the splitter was that it re-emitted section directives for every dynamic label found. The following was torn apart .symbol_stubs .indirect <symbol> L_<symbol>$stub: jmp *... L_<symbol>$stub_binder: ..somebinding code.. into .symbol_stubs .indirect_symbol <symbol> L_<symbol>$stub: jmp *... .symbol_stubs <--- NEW L_<symbol>$stub_binder: ..somebinding code.. This is incorrect as the Mac OS assembler enforces that every new code section that goes into .symbol_stubs is associated with the linker directive .indirect_symbol. This sanity check is obviously violated when we reemit .symbol_stub in the splitter. The solution is to ignore everything that ends with $stub_binder as new label, and chuck it into a single label for $stub. Also the splitter has to recognize .section __DATA... for the lazy_ptr indirection symbol. Adds a reminder to PositionIndependentCode.hs to take care of the splitter when the code generation is changed. This should not affect -fvia-c as the code generated by the C compiler is entirely different.