Fixes to LangRef.rst: incorrect attributes syntax and misplaced 'nobuiltin'

Patch by Stephen Lin


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179763 91177308-0d34-0410-b5e6-96231b3b80d8
Make this private method.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179764 91177308-0d34-0410-b5e6-96231b3b80d8
[ms-inline asm] Simplify some logic and add a FIXME for unhandled unary minus.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179765 91177308-0d34-0410-b5e6-96231b3b80d8
Fix grammar in LLVMBuild.rst


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179768 91177308-0d34-0410-b5e6-96231b3b80d8