Added bug compatibility for unicode decode mode when an old mysql client lib

is used: Set PIKE_BROKEN_MYSQL_UNICODE_MODE in the environment to get the
old buggy implementation in this case.

Also fixed a typo that caused the wrong unicode result wrapper to be used in
unicode decode mode.

Rev: lib/modules/Sql.pmod/mysql.pike:1.35
Rev: lib/modules/Sql.pmod/sql_util.pmod:1.17