Prior to this change, the libusbx52 Makefile was manually specifying the
pthread flags to indicate that the linker needed to link against the
pthread libraries.
This change moves the pthread detection logic out to configure.ac, and
updates the flags in libusbx52 Makefile to use the pthread compiler.
- libx52_init returns the libx52_device in an output parameter and
returns a libx52_error_code
- Make all functions return libx52_error_code
- Update package version to indicate incompatible API change
The conversion makes it simpler to allow cross-compilation, since we
should be using the host Python interpreter to build the generated
character map, rather than relying on the automake infrastructure.