As discussed in https://reviews.llvm.org/D24425 splitting the implementation of DW_AT_alignment into several patches. This one is a preparation that includes:
- Added alignment attribute to DIVariable family: modified DIGlobalVariable and DILocalVariable classes and their users (like DIBuilder)
- Added support for alignment in DI*Variable in bitcode. Had to perform a little workaround to support older bitcode versions (see BitcodeReader.cpp and BitcodeWriter.cpp)
- As discussed in https://reviews.llvm.org/D24425 renamed "AlignInBits" into "AlignInBytes" to match the fact that user specifies alignment in bytes in code and DWARF attribute also displays this value in bytes.