include/mysql.h:
  mysql_stmt_field_count() declaration
libmysql/libmysql.c:
  added mysql_stmt_field_count(): 
  we need this function to ease use of mysql_stmt_result_metadata:
  if mysql_stmt_field_count() != 0 mysql_stmt_result_metadata fails
  only if OOM.
libmysql/libmysql.def:
  declaration for mysql_stmt_field_count()