There is multiple use of class name
dd::Info_schema::MDL_deadlock_error_handler in two translation
units (table_stats.cc and tablespace_stats.cc). This is not
caught by usual compilation options and even by pb2 builds. The
problem was seen with the linker option -flto. This patch
combines both of implementation into class
Info_schema_error_handler and moved to translation unit
error_handler.cc.