[libclang] Expose record layout info via new libclang functions:

clang_Type_getAlignOf
clang_Type_getSizeOf
clang_Type_getOffsetOf
clang_Cursor_isBitField

Patch by Loïc Jaquemet!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179251 91177308-0d34-0410-b5e6-96231b3b80d8