ESC-237 No static init of LLAtomics and move TFRequest out of unnamed namespace.

Linux startup crash appears to be due to static/global C++ init of LLAtomic
types.  The initializer with explicit value makes some runtime calls and it
looks like these assume, at least on Linux, that apr_initialize() has been
called.  So move the static POST count to a member and provide accessors
and increment/decrement.  Command queue was built on a pointer to a class
in anonymous namespace and that's not quite valid.  Made it a nested
class (really a nested forward declaration) while keeping the derived
classes in anonymous.