llvm-mc: Various section parsing fixes.

 - Add missing flags for various Objective-C sections.

 - Fix names for [non_]lazy_symbol_pointer (these are misspelled in the manual).

 - .symbol_stub does not have the self modifying code flag set (this appears to
   be wrong in the manual?).

 - Add implicit alignment values; not yet used.

Also, call MCStreamer::Finish at the end of a successful parse.

llvm-svn: 79611