added characters that are special when within character
classes in a regular expression to the `escape(...)` call
when building `s:dirArrows`.
this does not fix when `' '` or `''` are your `dirArrows` and you
can't open up subdirs. i think that's an issue with how nerdtree
distinguishes things to traverse in the filetree.
Previously we highlighted symlinks as one item (NERDTreeLink):
symlinked_file -> /path/to/target
Split this out into 3 highlight groups:
* NERDTreeLinkFile
* NERDTreeLinkDir
* NERDTreeLinkTarget
So we have:
symlinked_dir/ -> /foo/bar
-------------- ***********
^ ^
| |
NERDTreeLinkDir NERDTreeLinkTarget
Similarly for file links - with NERDTreeLinkFile instead of
NERDTreeLinkDir.
This allows users to modify how symlinks are highlighted. E.g. to make
them appear as normal files/dirs they could add this to their vimrc:
hi link NERDTreeLinkFile NERDTreeFile
hi link NERDTreeLinkDir NERDTreeDir
hi link NERDTreeLinkTarget ignore
