DIBuilder: Delete dead code, NFC

There are two versions of `DIBuilder::createObjCIVar()`.  Delete the one
that's apparently dead.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218167 91177308-0d34-0410-b5e6-96231b3b80d8
Converting InstrProf's error_category to a ManagedStatic to avoid static constructors and destructors.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218168 91177308-0d34-0410-b5e6-96231b3b80d8
constify the TargetMachine being passed through the Mips subtarget
creation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218169 91177308-0d34-0410-b5e6-96231b3b80d8
[X86] Erase some obsolete comments from README.txt

I just tried reproducing some of the optimization failures in README.txt in the
X86 backend, and many of them could not be reproduced. In general the entire
file appears quite bit-rotted, whatever interesting parts remain should be
moved to bugzilla, and the rest deleted. I did not spend the time to do that,
so I just deleted the few I tried reproducing which are obsolete, to save some
time to whoever will find the courage to do it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218170 91177308-0d34-0410-b5e6-96231b3b80d8
Fix crash with an insertvalue that produces an empty object.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218171 91177308-0d34-0410-b5e6-96231b3b80d8