lib: media: add the media type to libvlc_media_new_callbacks()

Without this it's impossible to preparse the imem files. This is necessary if the result of preparse is used to set other callbacks like the amem and vmem ones, depending on the source data.

By default the type is unknown and preparsing is skipped in that case.

Draft: on top of !2870 (merged) to demonstrate the use of the new libvlc ABI versioning