test that sized deallocation really works before enabling it
test that sized deallocation really works before enabling it

Weirdly, some OSX compiler does allow -fsized-deallocation, yet barks
on any attempt to actually use it at compile time (!). So lets detect
this as well in configure and opt out as necessary.

Should fix issue #870.

rzinsly/gperftools,alk/gperftools,gperftools/gperftools,rzinsly/gperftools,gperftools/gperftools,chencl/gperftools,xiaoyur347/gperftools,rzinsly/gperftools,romange/gperftools,gperftools/gperftools,rzinsly/gperftools,alk/gperftools,xiaoyur347/gperftools,xiaoyur347/gperftools,alk/gperftools,acmorrow/gperftools,chencl/gperftools,acmorrow/gperftools,acmorrow/gperftools,chencl/gperftools,chencl/gperftools,romange/gperftools,acmorrow/gperftools,xiaoyur347/gperftools,alk/gperftools,romange/gperftools,romange/gperftools,gperftools/gperftools