Recommit "[DWARF] Add an api to get "interpreted" location lists"

This recommits 089c0f58, which was
reverted due to failing tests on big endian machines. It includes a fix
which I believe (I don't have BE machine) should fix this issue. The fix
consists of correcting the invocation DWARFYAML::EmitDebugSections,
which was missing one (default) function arguments, and so didn't
actually force the little-endian mode.

The original commit message follows.

Summary:
This patch adds DWARFDie::getLocations, which returns the location
expressions for a given attribute (typically DW_AT_location). It handles
both "inline" locations and references to the external location list
sections (currently only of the DW_FORM_sec_offset type). It is
implemented on top of DWARFUnit::findLoclistFromOffset, which is also
added in this patch. I tried to make their signatures similar to the
equivalent range list functionality.

The actual location list interpretation logic is in
DWARFLocationTable::visitAbsoluteLocationList. This part is not
equivalent to the range list code, but this deviation is motivated by a
desire to reuse the same location list parsing code within lldb.

The functionality is tested via a c++ unit test of the DWARFDie API.

Reviewers: dblaikie, JDevlieghere, SouraVX

Subscribers: mgorny, hiraditya, cmtice, probinson, llvm-commits, aprantl

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70394