Add per-direction wxSocket wait flags and byte counters.

Allow to specify whether the socket should block until all the data is read or
written or, on the contrary, avoid blocking only when reading or writing
instead of always using the same behaviour in both directions.

Also add separate counters for the bytes read/written instead of using the
same one for both.

These changes make it possible to use the same socket for reading/writing in
different threads.

Closes #14506.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72591 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -529,6 +529,8 @@ Major new features in this release
 
 All:
 
+- Add separate read/written bytes counters and per-direction NOWAIT and WAITALL
+  flags to wxSocket (Rob Bresalier).
 - Add wxDir::Close() method (Silverstorm82).
 - Fix compilation of wxHash{Map,Set} with g++ 4.7 (Nathan Ridge).
 - Fix posting large amounts of data in wxHTTP (Platonides).