Rename OMPT placeholder type names to be in the OMPT name space

r242052 changed the name of OMPT placeholder functions to move them from
the omp_ name space to the ompt_ name space. This patch moves the names of the
types of these functions into the OMPT name space as well.

Patch by John Mellor-Crummey

Differential Revision: http://reviews.llvm.org/D11171

llvm-svn: 242155