Portability fixes


client/mysqltest.c:
  Fixed that if error number 0 is included in --error, we will not generate an error message
include/mysql.h:
  Portability fix
mysql-test/mysql-test-run.sh:
  Portability fix
mysql-test/r/heap_btree.result:
  Portability fix
mysql-test/r/rpl_error_ignored_table.result:
  Portability fix
mysql-test/t/heap_btree.test:
  Portability fix
mysql-test/t/rpl_error_ignored_table.test:
  Portability fix
sql/sql_base.cc:
  simple optimzation
sql/sql_yacc.yy:
  simple optimzation