param: avoid spurious gcc warning about toksave possibly being uninitialized
frameencoder: match up integer argument types to avoid MSVC warning

The prototype in the WaveFront base class was:
   virtual void processRow(int row, int threadId) = 0;

Some versions of MSVC flag this as a warning
ratecontrol: fix cast of cutree offset, avoids MSVC warning
param: avoid spurious MSVC warning about buf being possibly uninitialized
encoder: avoid int64_t to int conversions, avoid more MSVC warnings
y4m: avoid implicit size_t to int conversion, avoid more MSVC warnings