[Fix #446] Make rust crate type customizable

Add an option to the rust checker so the user can set the value of the
--crate-type compiler flag
Reorder rust options alphabetically
First try at Ada support
First try at Fortran support
Make it work
Make it work
Fix ada warnings pattern
Partially fix formatting of gfortran
Various cleanups
Add note detecting Fortran compiler version
Clenaups
Fix comment indent
Use flycheck-ada-gcc-language-standard
Remove :error-filter for Ada and Fortran
Disable usage of flycheck-ada-gcc-language-standard for now
Add flycheck-fortran-gcc-language-standard
Default init language-standards for Ada & Fortran to strings
Better namings
Move f prefix to fortran standard variable
Use gfortran -std in the same way as other checkers