[clang][OpenMP][DebugInfo] Debug support for TLS variables present in OpenMP consruct

[clang][OpenMP][DebugInfo] Debug support for TLS variables present in OpenMP consruct

In case of OpenMP programs, thread local variables can be present in
any clause pertaining to OpenMP constructs, as we know that compiler
generates artificial functions and in some cases values are passed to
those artificial functions thru parameters. For an example, if thread
local variable is present in copyin clause (testcase attached with the
patch), parameter with same name is generated as parameter to artificial
function. When user inquires the thread Local variable, its debug info
is hidden by the parameter. User never gets the actual TLS variable
when inquires it, instead gets the artificial parameter.

Current patch suppresses the debug info for such artificial parameter to
enable correct debugging of TLS variables.

Reviewed By: aprantl

Differential Revision: https://reviews.llvm.org/D123787