DebugInfo: Use the comp_dir of the referencing type units when building debug_line.dwo

This isn't a complete fix - it falls back to non-comp_dir when multiple
compile units are in play. Adding a map of comp_dir to table is part of
the more general solution, but I gave up (in the short term) when I
realized I'd also have to calculate the size of each type unit so as to
produce correct DW_AT_stmt_list attributes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204202 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "Add back r203962, r204028 and r204059."

This reverts commit r204178.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204203 91177308-0d34-0410-b5e6-96231b3b80d8
When destroying a StringMap, just iterate over the map and destroy the contained elements.  Don't reset them back to 0 as their values aren't needed any more.  This results in ~StringMap() being mostly empty for POD types in BumpPtrAllocators

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204204 91177308-0d34-0410-b5e6-96231b3b80d8
Make the test harder by using a non-zero offset.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204205 91177308-0d34-0410-b5e6-96231b3b80d8