SlingboxLib: Fix alternative CSlingbox constructor

CSlingbox::CSlingbox(const char * szAddress, unsigned int uiPort /* = 5001 */) {
  // Call default constructor
  CSlingbox();
  ...
}

"CSlingbox();" - object is created and immediately removed.
Therefore with CSlingbox(const char * szAddress, unsigned int uiPort /* = 5001 */) class members will not be initialized.
[pvr] fix unnecessary creation of new CPVRChannel instances
[configure] libflac is not a hard dependency now
[linux] - update docs/README.*
Merge pull request #5282 from maksqwe/slingboxlib_fix

SlingboxLib: Fix alternative CSlingbox constructor
[slingbox] add .patch file after b3d686357d0912ce8c748bc013c93b0b6a47cd9b
Merge pull request #5527 from stefansaraev/flac

dont require libflac to build kodi core
dxva: fix selection of render target format
[keyboardlayouts] add Turkish
[vfs] Fix reading with zero size and null pointer
[vfs] Fix write with zero size and null pointer
[emu] Better emulate system read()/fread() functions
Merge pull request #5532 from queeup/keyboardlayouts

[keyboardlayouts] add Turkish
[vfs] PosixFile::Write(): remove unneeded cast
Merge pull request #5534 from Karlson2k/fix_vfs_and_emu_01

Better emulate system read() and fread() functions, fixes #15490
[rebrand][darwin/rebrand] - adapt readmes
[rebrand][packaging/seatbeltunlock] - renamed seatbeltunlock to be appnameagnostic, fix the pkg, make it org.xbmc.kodi-seatbeltunlock use @APP_NAME@
[rebrand][packaging/osx/ios/atv2] - move all package scripts to appname
agnostic folders, rename them to be appname agnostic and use @APP_NAME@ -
also add migration step in debian post-inst which will move XBMC data to Kodi if found
[rebrand][atv2] - rename the topshelf icon from XBMC.png to TopShelf.png
[rebrand][darwin] - make use of @APP_NAME@ in our build configurations