Add DebugInfo testcase for high_pc encoded as constant, fixed in r193555.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193711 91177308-0d34-0410-b5e6-96231b3b80d8
[Mips] Add more SHF_MIPS_xxx ELF section flags.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193713 91177308-0d34-0410-b5e6-96231b3b80d8
DebugInfo: Push header handling down into CompileUnit

This is a preliminary step to handling type units by abstracting over
all (type or compile) units.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193714 91177308-0d34-0410-b5e6-96231b3b80d8