llvm-mc: Various section parsing fixes.

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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@79611 91177308-0d34-0410-b5e6-96231b3b80d8