Improved CMake find module for Opus
More CMake find module improvements

The Speex find module is now implemented in the same way as the Opus
module.
Improved Opus module.
Improved CMake version check for Opus and Speex
Merge branch 'master' into afsk_com
More compatibility changes for the Speex and Opus find modules
Even more CMake compatibility changes
CMake version does not seem to match offered features
Merge branch 'master' on cubieboard

Conflicts:
	src/cmake/Modules/FindOpus.cmake
	src/cmake/Modules/FindSpeex.cmake
Implemented a NULL audio decoder
Bugfix in Async::AudioSelector

The selector did not work with some compiler optimizations turned on.
Bugfix in Async::{AudioSelector,DnsLookup,AudioSplitter}

Important code had been placed within assert statements. By default
CMake set compiler options that remove all assert statements when
compiling in release mode. This caused some things to stop working when
compiling for release.
Small bugfix in the Voter

If the squelch were open while quitting, a crash could occur.
Bugfix in CMake script for finding Opus and Speex

For Opus (and Speex) the version could not be found if the major version
were below 1.
New function Async::TcpConnection::setRecvBufLen

Now possible to change the buffer size of a TCP connection using
TcpConnection::setRecvBufLen.
Ignored some files generated by the old buildsystem
Fixed a warning in the "machine objects" (Macho) code
Tweaked compiler flags

Compiler warnings is now enabled in the same way as they were in the old
buildsystem. The NDEBUG flag was turned off since it remove asserts.
It's better to have the asserts left in the released code. Also removing
the asserts caused a lot of warnings about unused variables.
Updated the doxygen config files
Updated the README file
Bugfix in logfile handling

SvxLink would crash if the filesystem was full while trying to write to
the logfile.