This commit performs three related cleanups:
* The slvs library no longer uses explicit platform initialization
(which drags in the side effects of InitPlatform that are not
desirable in a library). Instead, it just ensures that it has
the temporary heap, which is what it was callingInitPlatform for.
* InitPlatform is simplified and moved to platform.cpp, next to
other path related functions.
* InitPlatform is renamed to InitCli and is called from InitGui
implementations. GUI toolkits sometimes have options they use
internally (that's the case for for GTK and Cocoa at least),
and we shouldn't try to parse those as a file to open.
whitequark