stagefright: misc fixes to software video encoders (and decoders)

- move logic to set encoder parameters to common encoder class
  (similarly to what was done for decoders)
- set compressed buffer size based on frame size and compression ratio,
  and codec-specific minimum size
- set raw buffer size based on frame size and metadata mode
- do not set stride and slice height on compressed ports
- advertise only QCIF support for google H263 encoder
- set large-enough input size for video decoders to support adaptive
  playback
- do not change input buffer size on output port reconfiguration, as
  no input buffer reallocation takes place
- do not return empty buffers with EOS after EOS has been signaled

Bug: 18513091
Bug: 18639027
Change-Id: Ib13492ef66adf331aa4572c67d2b283ea020cb41