Empty spaces in fortran lexer keyword recognition

[Anteru]

(Original issue 1484 created by anphi on 2018-11-14T20:37:47.258741+00:00)

Fortran allows arbitrary empty space to be embedded in keywords.
For example, it is legal to write "e n d d o"

While probably nobody would do this, and we don't want to request the lexer to handle that, some people run together certain multi-word keywords, such as "enddo" instead of "end do". The current Fortran lexer does not recognize such them. Could you please make any inter-word space for keywords optional, so that both versions are matched?