Added Subtarget support into RegisterInfo

Added Subtarget support into RegisterInfo
Added HasABICall and HasAbsoluteCall (equivalent to gcc -mabicall and
-mno-shared). HasAbsoluteCall is not implemented but HasABICall is the
default for o32 ABI. Now, both should help into a more accurate
relocation types implementation.
Added IsLinux is needed to choose between asm directives.
Instruction name strings cleanup.
AsmPrinter improved.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53551 91177308-0d34-0410-b5e6-96231b3b80d8