also improved filtering of the frame delta times.
while at it, improved interface of whrt backends to avoid leaking
implementation details.
This was SVN commit r6401.
whrt: output timer implementation info, fix assert ( 1/(x-epsilon) < 1/x
+ epsilon )
wsdl: fix slightly incorrect gamma values (first and last are now
exactly 0 and 1)
This was SVN commit r6321.