there was two problems about charsets in embedded server
1. mysys/charset.c - defined there default_charset_info variable is
modified by both server and client code (particularly when
--default-charset option is handled)
In embedded server we get two codelines modifying one variable.
I created separate default_client_charset_info for client code

2. mysql->charset and mysql->options.charset initialization isn't
properly done for embedded server - necessary calls added


include/sql_common.h:
  client charset info default declared
libmysqld/lib_sql.cc:
  thd_init_client_charset calls added
libmysqld/libmysqld.c:
  check_embedded_connection moved to client.c to avoid code duplication
sql-common/client.c:
  charset initialization moved to mysql_init_character_set to
  be used in embedded server
sql/sql_parse.cc:
  thread client charset initialization moved to thd_init_client_charset
  to avoid code duplication