Add the semantic checks for the OpenMP 4.5 - 2.15.3.3 Private clause.
1. Pointers with the INTENT(IN) attribute may not appear in a private clause.
2. Variables that appear in namelist statements may not appear in a private clause.
A flag 'InNamelist' is added to the Symbol::Flag to identify the symbols
in Namelist statemnts.
Test cases : omp-private01.f90, omp-private02.f90
Reviewed By: kiranchandramohan
Differential Revision: https://reviews.llvm.org/D90210
Praveen G