DebugInfo: Move type units into the debug_types section with appropriate comdat grouping and type unit headers

This commit does not complete the type units feature - there are issues
around fission support (skeletal type units, pubtypes/pubnames) and
hashing of some types including those containing references to types in
other type units.

Originally committed as r197073 and reverted in r197079.

This commit originally got jumbled up with another build-breaking commit
and I can't find the failures I thought this caused anymore.
Recommitting to hopefully get some clean buildbot results to work from.
I have a sneaking suspicion there's unstable output in the comdat group
output of MCStreamer...

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197197 91177308-0d34-0410-b5e6-96231b3b80d8
llvm-cov: Added -b option for branch probabilities.

This option tells llvm-cov to print out branch probabilities when
a basic block contains multiple branches. It also prints out some
function summary info including the number of times the function enters,
the percent of time it returns, and how many blocks were executed.

Also updated tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197198 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "DebugInfo: Move type units into the debug_types section with appropriate comdat grouping and type unit headers"

This reverts commit r197197.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197199 91177308-0d34-0410-b5e6-96231b3b80d8