libcouchbase - update 2.4.5 with FPE patch

This is the normal 2.4.5 release with a one-liner fix for FPEs caused as
a result of misuse of mach_absolute_time(). This fix is specific for
Macs

In the next cycle I'll enable proper tests as part of the build process, so silly trivial issues like this will be caught earlier.
This needs a new version number.