Fortran-language-server

Improvements
* Add initial implementation of simple preprocessor, ref [78](https://github.com/hansec/fortran-language-server/issues/78)

Fixes
* Updated Fixed/Free detection logic using ampersands to check for comment line, fixes [81](https://github.com/hansec/fortran-language-server/issues/81)
* Support use of "END" as a variable, fixes [82](https://github.com/hansec/fortran-language-server/issues/82)

Fixes
* Add support for named "SELECT" statements, fixes [80](https://github.com/hansec/fortran-language-server/issues/80)
* Track scopes for "ASSIGNMENT" and "OPERATOR" interface statements, fixes [79](https://github.com/hansec/fortran-language-server/issues/79)
* Fix bug in parsing "SELECT" statements with no space, fixes [77](https://github.com/hansec/fortran-language-server/issues/77)
* Further improve discrimination between end statements and other items, ref [73](https://github.com/hansec/fortran-language-server/issues/73)

Fixes
* Normalize file paths when storing/accessing file index, fixes [75](https://github.com/hansec/fortran-language-server/issues/75)
* Fix intrinsic statement "COUNT" ([76](https://github.com/hansec/fortran-language-server/pull/76))

Fixes
* Further improve discrimination between end statements and variables/block labels, ref [73](https://github.com/hansec/fortran-language-server/issues/73)
* Fix autocomplete errors when ASSOCIATE and ENUM statements are present
* Fix severity reporting with "debug_diagnostics" command line option

Fixes
* Fix discrimination between end statements and variables with underscores, fixes [73](https://github.com/hansec/fortran-language-server/issues/73)
* Detect enum definitions, fixes [74](https://github.com/hansec/fortran-language-server/issues/74)

Fixes
* Detect and support associate statements, fixes [72](https://github.com/hansec/fortran-language-server/issues/72)