include: add missing types in headers and check them

Otherwise, the header cannot be included as a standalone header and the correct inclusion order must be used.

TODO:

• missing license in test/libvlc/include.c
• remove header build tests from TESTS
• better layout of the shared types/enum?
• split of the libvlc_event_type_t /libvlc_event_state_t enums ?
• vlc core headers
• libvlc headers
• macosx changes for vlc_config_cat (ref !4083 (merged))