THRIFT-736. cpp: Check for availability of pthread_mutex_timedlock

r920679 introduced a call to pthread_mutex_timedlock, which is not
available on all UNIX variants.  In particular, it is missing on Mac OS.
Add a preprocessor check for the relevant feature macro.  If it fails,
just use a trylock.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@925940 13f79535-47bb-0310-9956-ffa450edef68
1 file changed