Don't emit relocs for the __eh_frame section as they can be implicit.

The __eh_frame section contains relocations which can always be implicitly generated.

This patch tracks whether sections have only implicitly relocations and skips emitting them to the object file if that is the case.

The test case here ensures that this is the case for __eh_frame sections.

Reviewed by Lang Hames.

http://reviews.llvm.org/D15594

llvm-svn: 257099