Fix the partial backtrace when using a combination of stripped function symbols
and -fomit-frame-pointer.

- Parses eh_frame FDEs to determine the function address and size so that
the call frame parsing can continue.

Note: This code path is specific to ELF and PECOFF, because ObjectFileMachO
uses LCT_FunctionStarts to efficiently populate the symbol table.

Thanks to Jason Molenda for the review!


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@186585 91177308-0d34-0410-b5e6-96231b3b80d8