Fixing srt_getsockopt for bool socket options

[maxsharabayko]

In srt_getsockopt(..) API function these bool socket options were actually using int type when casting the optval, which may lead to writing outsize the memory of the optval when bool is provided.

• SRTO_SENDER
• SRTO_TSBPDMODE
• SRTO_DRIFTTRACER
• SRTO_ENFORCEDENCRYPTION

This PR changes types to bool if optlen is zero of sizeof(bool), otherwise casts to int.

ABI Change

Fixing cast to bool is the lesser evil compared to potential outside-of-memory writing.
This change however affects SRT API a bit and might lead to certain upgrading difficulties.
Both FFMpeg and GStreamer should not get into trouble with this change, as they only get the value of SRTO_PAYLOADSIZE.

Still, the output optlen should provide a hint of how many bytes were actually set by srt_getsockopt(..) function.

Note that the type used to set those bool options is still int there, as both int and bool types are supported in srt_setsockopt(..).

TODO

• Consider if this breaks ABI compatibility with previous SRT versions
• Check srt_getopt for SRTO_TLPKTDROP: does not use the value from config (to be addressed separately).

[maxsharabayko]

Reverted the second commit, which was taking the optlen value into account. ☝️

[maxsharabayko]

Related documentation. PR #1941: add an instruction to provide optval size in optlen when calling srt_getsockopt(..).