[MediaPortal pvr addon] Gotham update to v.1.9.12 (bugfixes)

This PR contains a subset from PR #283. No new features, only fixes and warning/error log improvements.

Changelog v1.9.12
- Added: Live TV/Recordings: Report "permission denied" errors on SMB access failures
- Changed: [Settings] enable fast channel switching by default
- Changed: Reduce the signal status calls to once every 10s.
- Fixed: Channel thumbnails: replace also the invalid file name characters <>*?\| in the channel name by a _
- Fixed: [SMB] Allow an empty username and password field
- Fixed: [SMB] Don't replace \\ by smb:// when not at the start of the path
- Fixed: Stop timeshifting at the backend side on buffer open failure.
- Fixed: gcc/CPPcheck warnings