Currently DIBasicType uses two flags DIFlagBigEndian and DIFlagLittleEndian, this patch separates it to DIBTFlags.
DIBTFlags have two flags in this patch, DIBTFlagBigEndian and DIFlagLittleEndian.
This patch is in response for review https://reviews.llvm.org/D73861
After this patch, two more flags will be added in DIBTFlags.
The bitcode test is not present for DIBasicType with BigEndian/LittleEndian flags. this patch adds it.