This change adds additional compiler warnings as detected by the
autoconf archive. Because the code is susceptible to these additional
warnings, disable treating warnings as errors for now, until we can fix
the warnings.
The hope was that I could compile some tests that would override
libx52_vendor_command, and run those on OSX to bypass the skipped tests
that used x52cli. However, a Travis-CI run indicated that the compiler
on OSX doesn't support weak symbols, which renders the point moot.
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.
nirenjan