[OPENMP] Improved code for generating debug info + generation of all OpenMP...

[OPENMP] Improved code for generating debug info + generation of all OpenMP regions in termination scope
Patch adds proper generation of debug info for all OpenMP regions. Also, all OpenMP regions are generated in a termination scope, because standard does not allow to throw exceptions out of structured blocks, associated with the OpenMP regions
Differential Revision: http://reviews.llvm.org/D7935

llvm-svn: 231757