runtime(doc): Replace rotted URL links

runtime(doc): Replace rotted URL links

Both links to libXpm and mysyntax.vim are up but the listed
libXpm version is not offered anymore and mysyntax.vim is no
longer served at all.  The link for searching dictionary
extensions of Apache OpenOffice is broken; an alternative
link can be discovered from the home page.  Finally, the
English dictionaries Apache OpenOffice extension is probably
gone for good (is it incompatible with more recent versions
of the suite?) as its page neither available directly nor
discoverable through search.

closes: 18549

Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>