[DebugInfo] Apply subprogram attributes on behalf of owner CU

When using full LTO it is possible that template function definition DIE
is bound to one compilation unit and it's declaration to another. We should
add function declaration attributes on behalf of its owner CU otherwise
we may end up with malformed file identifier in function declaration 
DW_AT_decl_file attribute.

Differential revision: https://reviews.llvm.org/D58538

llvm-svn: 354978