Since commit v3.5.0-rc1~241^2~1 (cmFortranParser: Parse #line
directives, 2015-11-02) our Fortran dependency scanner parses `#line`
directives to extract the named files. However, some compilers produce
`#line` directives that name directories instead of files. Work around
such cases by verifying that the extracted path names a file and not a
directory.
Teach the lexer to extract the #line directive prefix and line number as
a new token type. Teach the parser to recognize this token followed by
a string as the file name (plus possibly other content). Report the
named file as included by the source file.
Brad King