v9.0.0 of prep

The code was refactored heavily as part of a long-term modernization of the code. The largest change was that the expression parser for LOGICAL and INTEGER expressions used in the conditional directives ($IF/$ELSEIF/$IFDEF....) was placed in it's own module (M_expr).

Functionality should remain upper-compatible with previous versions.

v8.1.1 of prep(1) - a Fortran preprocessor

v8.1.1 of prep(1) - a Fortran preprocessor; with rewritten documenation.

V8.0.0 release of prep(1) - the Fortran preprocessor

Expressions now handle negative values correctly, added some syntactic sugar such as allowing multiple declarations on $DEFINE, and allowing $SHOW to just show specified values, and rewrote the documentation. See CHANGELOG.md for a description of major changes.

prep(1) Fortran pre-processor Version 6.0.0

prep(1) is a Fortran pre-processor written in Fortran.

Full Changelog: `https://github.com/urbanjost/prep/commits/v6.0.0```

2021-12-28 @urbanjost