XCore target: Add large code model

XCore target: Add large code model

When using large code model:
Global objects larger than 'CodeModelLargeSize' bytes are placed in sections named with a trailing ".large"
The folded global address of such objects are lowered into the const pool.

During inspection it was noted that LowerConstantPool() was using a default offset of zero.
A fix was made, but due to only offsets of zero being generated, testing only verifies the change is not detrimental.

Correct the flags emitted for explicitly specified sections.

We assume the size of the object queried by getSectionForConstant() is never greater than CodeModelLargeSize.
To handle greater than CodeModelLargeSize, changes to AsmPrinter would be required.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196087 91177308-0d34-0410-b5e6-96231b3b80d8