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.
a `version 2.4.5_1_gd7f6ecf` line below here.