rdpgfx: various fixes according to comments

rdpgfx: various fixes according to comments
1. Fix stream leak in rdpgfx
2. Make src data const in zgfx. Harden zgfx to be independent to byte order
3. Fix written bytes return value in channel write
4. Add check for return value in shadow_client.c
5. Add gfx callback to send surface command with frame marker pdu.
6. Check remain length for recv subroutine
7. Fix compile errors