move sources to src/
extract bitmap surface related code to api-bitmap-surface.c
extract output surface related code to api-output-surface.c
extract video surface related code to api-video-surface.c
extract video mixer related code to api-video-mixer.c
rename vdpau-decoder.c and vdpau-presentation.c
more file renames
extract remaining functions into api-csc-matrix.c and api-device.c
rename vdpau-soft.h to api.h
fix header double inclusion guards