use a wrapper for cvCreateVideoWriter using cvSize

supposedly the old way (two CInt arguments) used to work in some cases,
but this did not work (cvVideoWriter returned a null pointer) for
my system. Note that there are similar wrappers pre-existing
in HOpenCV_wrap.c
Merge github.com:aavogt/HOpenCV
Merge pull request #1 from aavogt/master

add a cvCreateVideo wrapper