Add an encoder method for encoding the SPS/PPS without encoding a frame

This is useful if using a muxer that requires the SPS/PPS to be
available before the first frame is encoded.
Convert some assembly files to unix newlines

This makes them consistent with the rest of them.
Get rid of trailing whitespace in the assembly source files
Merge pull request #97 from mstorsjo/asm-source-cleanup

Make all asm sources consistently use unix newlines and remove trailing whitespace
Merge pull request #134 from mstorsjo/encode-sps-pps

Add an encoder method for encoding the SPS/PPS without encoding a frame