[flang] Changed CFI_CDESC_T c++ macro and various other comment fixes

 -  CFI_CDESC_T can now be cast to CFI_cdesc_t without using
    reinterpret_cast.
 -  Use {} initialization everywhere according to style guideline
 -  Avoid useless parentheses
 -  Do not use static storage when useless in tests.
 -  Reodered some loops that were confusing in tests

Original-commit: flang-compiler/f18@d0ed631dfdabfb162e3518f7e950ea4f9853c71a
Reviewed-on: https://github.com/flang-compiler/f18/pull/227
Tree-same-pre-rewrite: false