api: drop param.vui.bEnableVuiParametersPresentFlag and bEnableAspectRatioIdc

These two params can be implied from other parameters, and having them present
only makes the VUI configuration more complicated than it needs to be.

This commit also drops the debugging --vui CLI option
strtok_r: fix detection on Windows

* Make sure HAVE_STRTOK_R is always defined, to 0 if absent
* Fix typo in #if
* mingw-w64's pthread.h #defines strtok_r, make sure to undef it
before we use our own definition.