X86: Change FTAG register size in FXSAVE structure

Summary:
 - Changed from 16 bits to 8 bits for Intel Architecture
    -- FXSAVE structure now conforms with the layout of FXSAVE
       area specified by IA Architecture Software Developer Manual

 - Modified Linux and FreeBSD specific files to support this change
    -- MacOSX already uses 8 bits for ftag register

 - Modified TestRegisters.py and a.cpp:
    -- Change allows 8 bit comparison of ftag values

    -- Change resolves Bug 24733:
       Removed XFAIL for Clang as the test works and passes for
       Clang compiler as well

    -- Change provides a Generic/Better way of testing Bug 24457
       and Bug 25050 by using 'int3' inline assembly in inferior

Signed-off-by: Abhishek Aggarwal <abhishek.a.aggarwal@intel.com>

Reviewers: ovyalov, jingham, clayborg

Subscribers: tfiala, emaste

Differential Revision: http://reviews.llvm.org/D13587

llvm-svn: 250022