xcmp/cmsColNm.c cleanup of static allocations

[Martti Kühne]

Hello list,

As I haven't checked whether any more current version of xlib exposes
this issue, I went with the assumption that 1.6.3 was a recent enough
state of libx11. here's what I found:

There are two statically declared memory hunks 'strings' and 'pairs'
in xcmp/cmsColNm.c that allocate storage but don't release it on the
client side. I wrote a very crude patch to overcome the issue and can
run my xlib dependent app through valgrind without seeing [1]. I
haven't found a better place for it, and it would probably better be
kept in ClDisplay.c, but as the codebase doesn't implement internal
extensions, this was where I put it. There might be implications for
multithreaded code and code using multiple colormaps, but I let these
issues slip for now.

cheers!
mar77i

[0] https://gist.github.com/mar77i/bda1c64f0e1797a6d53c
[1] https://gist.github.com/mar77i/975ec116cb91ff5086dd