DebugInfo: Include the decl_line/decl_file in subprogram definitions if they...

DebugInfo: Include the decl_line/decl_file in subprogram definitions if they differ from those in the declaration

This is handy for some AutoFDO stuff, and seems like a minor improvement
to correctness (otherwise a debug info consumer might think the decl
line/file of the def was the same as that of the declaration - though
what a consumer might use that for, I'm not sure - maybe "list <func>"
would've misbehaved with the old behavior?) and at a minor cost (in my
experiment, with fission, without type units, without compression, 0.01%
growth in debug info in the executable/objects, 0.02% growth in the .dwo
files).

llvm-svn: 249487