This patch introduces a new helper class OMPBuilderCBHelpers,
which will contain all reusable C/C++ language specific function-
alities required by the OMPIRBuilder.
Initially, this helper class contains the body and finalization
codegen functionalities implemented using callbacks which were
moved here for reusability among the different directives
implemented in the OMPIRBuilder, along with RAIIs for preserving
state prior to emitting outlined and/or inlined OpenMP regions.
In the future this helper class will also contain all the different
call backs required by OpenMP clauses/variable privatization.