Fix mismatched oc_mb_fill_cmapping11 signature.

oc_mb_fill_cmapping11() was defined without the last two parameters
 of its fellow mapping functions, meaning it got called with extra
 undeclared parameters.

This could confuse the emscripten JavaScript cross-compiler's asm.js
 optimizations, as it's very picky about function signatures.

Fixes #2068.
Patch by Brion Vibber <brion@pobox.com>.

svn path=/trunk/theora/; revision=19261