Use Formal Lexer / Parser for Fortran syntax

[v1kko]

Currently we are using a simple text-based parser
If we want to make the tool more robust we can think of using an antlr or sdf based tool (f77 syntax already supported)

• https://github.com/antlr/grammars-v4/tree/master/fortran77
• http://fortran-parser.sourceforge.net/ (antlr, f2008)
• https://github.com/OpenFortranProject/ofp-sdf (sdf, new version of fortran parser)