Kill the libreofficekit static library / shim.c.

It looks like the cleanest method of getting lok_init into
the LibreOfficeKit.h header (in a c89 compatible way) is to
have it as a static function. Unfortunately this provokes
unused function warnings where lok_init doesn't get used.

(inline is only available in C99 or later -- this is actually
 available on Linux which is the only place that we can actually
 use lok_init anyways currently, however given we have to keep
 c89 for the C code (for MSVC) compatibility, selectively enabling
 c99 would likely be more messy.)

Change-Id: I0493e7a68ed5397479220bb6ba8c3db870b6dd32
DO NOT MERGE: reenable LOK tiled rendering test (BRANCH ONLY).

Change-Id: Ica4e570cafa25f4c642016608d8d510e668ed701