DebugInfo: Introduce the notion of "form classes"

Summary:
Use DWARF4 table of form classes to fetch attributes from DIE
in a more consistent way. This shouldn't change the functionality and
serves as a refactoring for upcoming change: DW_AT_high_pc has different
semantics depending on its form class.

Reviewers: dblaikie, echristo

Reviewed By: echristo

CC: echristo, llvm-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1961

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193553 91177308-0d34-0410-b5e6-96231b3b80d8
DWARF parser: since DWARF4, DW_AT_high_pc may be a constant representing function size

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193555 91177308-0d34-0410-b5e6-96231b3b80d8
Quote potential shell expansions found in tests

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193558 91177308-0d34-0410-b5e6-96231b3b80d8
lit: add missing substitutions for recently added tools

llvm-mcmarkup, obj2yaml and yaml2obj were missing from the substitutions list,
causing the test suite to fail in a sandboxed environment.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193559 91177308-0d34-0410-b5e6-96231b3b80d8
DWARF parser: Use ArrayRef to represent form sizes and simplify DWARFDIE::extractFast() interface. No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193560 91177308-0d34-0410-b5e6-96231b3b80d8
Renaming MCJIT .ir files to .ll and moving them to Inputs

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193562 91177308-0d34-0410-b5e6-96231b3b80d8