Refactor xsetcolorname()
I mainly improved the slightly off algorithm used to load colours in the 256-colour-space and
removed unnecessary local values (r,g,b,colour).
"colour" is not necessary as a punchbag for XftColorAlloc[Value,Name], as they don't mess with
the result-adress until they are absolutely sure everything worked out[0].
Being at it, I changed the error-returns for AllocValue to dies (just like in xloadcols()), as
a failure is most likely an OOM-situation you better catch early.
In case of an invalid name everything stays the same.
[0]: http://www.opensource.apple.com/source/X11libs/X11libs-40/libXft/libXft-2.1.13/src/xftcolor.c
Signed-off-by: Christoph Lohmann <20h@r-36.net>
