Add parens and brackets to folded delimiters.
Conditionally define keywords for if, else, elseif, etc. so they can be used inside of folds.
Folding for if..elseif..else

Note: can't figure out how to get the } delimiter before the else and elseif to highlight differently than the
else/elseif, so for now they are highlight as a keyword instead of delimiter.
Folding while and do/while loops.
Added for loop folding.
Added folding for foreach loops
Improved folding for try/catch/finally
Added folding for switch/case/default.
Updated folding option description and cleaned up option checking.
Folding for heredocs and nowdocs.

I don't like that I basically copied all of the definitions for these and added 'fold' to the end, but I couldn't
figure out a different way to conditionally add folding that didn't involve complete redeclaring them.
All folding regions contain the necessary clusters/regions so that they properly nest.

I also changed the highlight link for phpException to be Exception since it didn't make sense to have
try/catch/finally be one color sometimes and another other times.
Fold HEREDOCs without repeating code.
Merge branch 'swekaj/fold-enhancements'
Folding: {Doc => Syn}Fold, after syntax/yacc.vim.

Avoid potential clash with user-defined commands. SynFold is specific to
the syntax.

Check if Vim has been compiled with 'folding' support as well.
Docker: Don't add the syntax file in the container.

Use host volumes to bind the plug-in directory as /var/php. This allows
us to change the syntax file without rebuilding the container.
PHP 5.6.0RC2