LCC: Support Fortran for lcc/lfortran < 1.24
As CMake started to successfully detect and use Fortran on LCC 1.23 (and probably lower), several fixes were required:
- Don't require 'liblfortran' on LCC < 1.24 (there is no such library there)
- Don't test broken name mangling with FortranCInterface
- Don't test preprocessing of Fortran files if it's not supported
All changes are a subject only to Fortran compiler from MCST LCC suite < 1.24. Tested with LCC 1.23.19, 1.25.17, 1.26.16.