Swap these siconify height/width's back to preprocessor macros to
avoid freaky corners of C.  Change them to uppercase to keep out of
harms way a bit better.
The only place this is used, it needs to be a non-const signed char,
so don't fight it.
Revert r331 turning these back into vars, but move them into iconmgr
and eliminate the need for siconify.h wholesale.