MYSQL_VERSION_ID is tested before it has been defined.  This leads to
a warning when compiling with -Wundef and it also will break the
internal logic of mysql_com.h as soon as MYSQL_VERSION_ID exceeds
50000.

The fix entailed a simple re-ordering of included files in mysql.h


include/mysql.h:
  Fix for Bug #20246 (enum mysql_enum_shutdown_level not well-defined in mysql_com.h)
  
  MYSQL_VERSION_ID is tested before it has been defined.  This leads to
  a warning when compiling with -Wundef and it also will break the
  internal logic of mysql_com.h as soon as MYSQL_VERSION_ID exceeds
  50000.
  
  Placed the #include for mysql_version.h above mysql_com.h to resolve conflict