Rip out the 'is temporary' nonsense from the MCContext interface to

Rip out the 'is temporary' nonsense from the MCContext interface to
create symbols.  It is extremely error prone and a source of a lot
of the remaining integrated assembler bugs on x86-64.

This fixes rdar://7807601.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@99902 91177308-0d34-0410-b5e6-96231b3b80d8