[cmake-developers] Improving Vim support in CMake

[Ben Boeckel]

Hi all,

Any Vim users out there who would like to try out the changes I've made
to the Vim files shipped with CMake can grab it from either stage
(vim-support-overhaul) or my GitHub fork[1]. It is not in next yet since
I expect further changes to come and that would only make unnecessary
churn on the dashboards.

List of improvements to the syntax file:

  - drop support for < 7.0 (which is 7.5 years old now);
  - add support for Lua-style comments;
  - update the list of system variables;
  - update the list of operators;
  - make only commands case-insensitive;
  - update the list of built-in commands (and deprecated ones);
  - highlight user-defined function and macro calls; and
  - tweak colors a bit.

One thing which was also changed that isn't in that list (from the
commit message) is that deprecated commands are now highlighted as
WarningMsg so they stand out.

The cmake-help code has also been changed to use 'K' rather than <F1> to
get help about a command (and the global binding was removed since I
don't expect it is used much and it's only going to be a surprise).

I don't have enough experience with indentation logic, but that also
needs some work.

Testers and comments welcome :) .

--Ben

[1]https://github.com/mathstuf/CMake/tree/vim-support-overhaul