Reduce output size of Skin::makeVariablesScript() for the head variables.

Reduce output size of Skin::makeVariablesScript() for the head variables.
Drops a lot of unnecessary whitespace (but keeps newlines for legibility) and puts multiple defs into a single 'var' statement.
Reduces the head vars script from 1485 bytes to 1201 (nearly 20% savings), though this is of course reduced with gzipping (27 bytes, 4%). Cutting those bytes out of *every dang request* doesn't hurt though. :)