Fix syntax highlighting for bracket arguments and comments

[namniav]

Auxiliary/vim/syntax/cmake.vim incorrectly defines cmakeBracketArguement, cmakeComment and cmakeBracketArgument as

syn region cmakeBracketArgument start="\[\z(=\?\|=[0-9]*\)\[" end="\]\z1\]" contains=cmakeTodo,@Spell
syn region cmakeComment start="#" end="$" contains=cmakeTodo,@Spell
syn region cmakeBracketComment start="\[\z(=*\)\[" end="\]\z1\]" contains=cmakeTodo,@Spell

cmakeBracketArgument doesn't match valid bracket argument containing more than one = in opening bracket, e.g., [==[...]==], and mismatches invalid text such as [=0123[...]=0123].

cmakeBracketComment should start with #.

cmakeComment mismatches and overrides bracket comment.

The correct syntaxs should look like

syn region cmakeBracketArgument start="\[\z(=*\)\[" end="\]\z1\]" contains=cmakeTodo,@Spell
syn region cmakeComment start="#\(\[=*\[\)\@!" end="$" contains=cmakeTodo,@Spell
syn region cmakeBracketComment start="#\[\z(=*\)\[" end="\]\z1\]" contains=cmakeTodo,@Spell

The change in syntax/cmake.vim is going to be merged into CMake: merge request and issue.