Add "lfortran" and version into all mod file names

See here for a background:

https://fortran-lang.discourse.group/t/installing-fortran-module-files/1135/15

Instead of a.f90 -> a.mod, it should be lfortran-a.mod or a.lfortran-001400.mod, that way module files can coexist with other compilers and it makes it more robust. It's also what Python does: a.py -> __pycache__/a.cpython-39.pyc.