[clang] [flang] [flang][semantics] Add a flag to relax some of the semantic constraints on C_LOC (PR #195112)

[Kiran Chandramohan via cfe-commits]

kiranchandramohan wrote:

Note: I am moving the Fortran/Flang only options to a separate file in https://github.com/llvm/llvm-project/pull/194398. 

https://github.com/llvm/llvm-project/pull/195112