MHEG: Cache database lookups in GetChannelIndex

Signed-off-by: Lawrence Rust <lvr@softsystem.co.uk>
Signed-off-by: Stuart Morgan <smorgan@mythtv.org>
(cherry picked from commit b9e576fac0d253806711292b2535e8f33e9c7579)
MHEG: allow escape key to exit liveTV in input register 5

Signed-off-by: Lawrence Rust <lvr@softsystem.co.uk>
Signed-off-by: Stuart Morgan <smorgan@mythtv.org>
(cherry picked from commit 7fa6f2339f35674432e615770cf1d73f4e23caac)
Don't try to pop an entry from an empty list in SSDP::ProcessData. Inspired by patch from Lawrence Rust but changed to use IsEmpty() instead of size()
(cherry picked from commit bb6e3a0daf1a2a2c15549dc4ce9446c196c37569)