Basic Async MySQL Client Support

Summary:
WebScaleSQL Feature: Async Client

This diff builds loosely upon the 5.1 client work at Facebook, and
brings async to 5.6.  It is not fully feature complete (no SSL. no
compression, only supports the default native auth) but it is a good
first step, is sufficient for our needs, and we can extend it.

This also adds a #define to indicate the nonblocking client is available.

This changes slightly the ABI and so it also renames 'libmysqlclient' to
'libwebscalesqlclient' -- however, this is compatible with almost every
use case (changes are additive only, but do include changes to some data
structures).

Test Plan:
mtr, testing against internal tools

Also, tested building with:
* clang-3.5 with "-Wno-deprecated-register".
* gcc-4.9

Reviewers: chip, inaam-rana, pivanof, darnaut, jeremycole, weixiang.zhai

Reviewed By: jeremycole, inaam-rana, pivanof, chip, weixiang.zhai

Subscribers: fe, darnaut, methane, steaphan, atcurtis, chip, liang.guo.752, andrew-ford, jeremycole, flamingcow, MarkCallaghan, jtolmer

Differential Revision: https://reviews.facebook.net/D17031
Differential Revision: https://reviews.facebook.net/D33777
Differential Revision: https://reviews.facebook.net/D33801
Differential Revision: https://reviews.facebook.net/D36153

client/CMakeLists.txt

@@ -33,48 +33,48 @@ COPY_OPENSSL_DLLS(copy_openssl_client)
 
 ADD_DEFINITIONS(${SSL_DEFINES})
 MYSQL_ADD_EXECUTABLE(mysql completion_hash.cc mysql.cc readline.cc sql_string.cc)
-TARGET_LINK_LIBRARIES(mysql mysqlclient)
+TARGET_LINK_LIBRARIES(mysql webscalesqlclient)
 IF(UNIX)
   TARGET_LINK_LIBRARIES(mysql ${READLINE_LIBRARY} ${CURSES_LIBRARY})
 ENDIF(UNIX)
 
 MYSQL_ADD_EXECUTABLE(mysqltest mysqltest.cc COMPONENT Test)
 SET_SOURCE_FILES_PROPERTIES(mysqltest.cc PROPERTIES COMPILE_FLAGS "-DTHREADS")
-TARGET_LINK_LIBRARIES(mysqltest mysqlclient regex)
+TARGET_LINK_LIBRARIES(mysqltest webscalesqlclient regex)
 
 
 MYSQL_ADD_EXECUTABLE(mysqlcheck mysqlcheck.c)
-TARGET_LINK_LIBRARIES(mysqlcheck mysqlclient)
+TARGET_LINK_LIBRARIES(mysqlcheck webscalesqlclient)
 
 MYSQL_ADD_EXECUTABLE(mysqldump mysqldump.c ../sql-common/my_user.c)
-TARGET_LINK_LIBRARIES(mysqldump mysqlclient)
+TARGET_LINK_LIBRARIES(mysqldump webscalesqlclient)
 
 MYSQL_ADD_EXECUTABLE(mysqlimport mysqlimport.c)
 SET_SOURCE_FILES_PROPERTIES(mysqlimport.c PROPERTIES COMPILE_FLAGS "-DTHREADS")
-TARGET_LINK_LIBRARIES(mysqlimport mysqlclient)
+TARGET_LINK_LIBRARIES(mysqlimport webscalesqlclient)
 
 MYSQL_ADD_EXECUTABLE(mysql_upgrade mysql_upgrade.c)
-TARGET_LINK_LIBRARIES(mysql_upgrade mysqlclient)
+TARGET_LINK_LIBRARIES(mysql_upgrade webscalesqlclient)
 ADD_DEPENDENCIES(mysql_upgrade GenFixPrivs)
 
 MYSQL_ADD_EXECUTABLE(mysqlshow mysqlshow.c)
-TARGET_LINK_LIBRARIES(mysqlshow mysqlclient)
+TARGET_LINK_LIBRARIES(mysqlshow webscalesqlclient)
 
 MYSQL_ADD_EXECUTABLE(mysql_plugin mysql_plugin.c)
-TARGET_LINK_LIBRARIES(mysql_plugin mysqlclient)
+TARGET_LINK_LIBRARIES(mysql_plugin webscalesqlclient)
 
 MYSQL_ADD_EXECUTABLE(mysqlbinlog mysqlbinlog.cc)
-TARGET_LINK_LIBRARIES(mysqlbinlog mysqlclient semisync_slave_client)
+TARGET_LINK_LIBRARIES(mysqlbinlog webscalesqlclient semisync_slave_client)
 
 MYSQL_ADD_EXECUTABLE(mysqladmin mysqladmin.cc)
-TARGET_LINK_LIBRARIES(mysqladmin mysqlclient)
+TARGET_LINK_LIBRARIES(mysqladmin webscalesqlclient)
 
 MYSQL_ADD_EXECUTABLE(mysqlslap mysqlslap.c)
 SET_SOURCE_FILES_PROPERTIES(mysqlslap.c PROPERTIES COMPILE_FLAGS "-DTHREADS")
-TARGET_LINK_LIBRARIES(mysqlslap mysqlclient)
+TARGET_LINK_LIBRARIES(mysqlslap webscalesqlclient)
 
 MYSQL_ADD_EXECUTABLE(mysql_config_editor mysql_config_editor.cc)
-TARGET_LINK_LIBRARIES(mysql_config_editor mysqlclient)
+TARGET_LINK_LIBRARIES(mysql_config_editor webscalesqlclient)
 
 # "WIN32" also covers 64 bit. "echo" is used in some files below "mysql-test/".
 IF(WIN32)