cleanup: initialize local variables to avoid gcc warning

gcc thinks there's a control flow path that can access these variables
without them having been assigned a value.  I don't think there is, but
initialize them anyway.
autoconf: detect available headers and avoid redeclaring libc types

If we have struct timeval in the libc headers, it's best to use it
instead of assume the CC3000 library can declare its own.
Regenerate autoconf support files
socket: fix result type of ntohs/htons
cc3000_common: provide identifier to detect release version

Some applications rely on bug fixes made to the repackaged release; make
it possible to determine which version is being used.
README.md: document new versioning feature and content changes