Tree cleaup after the last major merges in mysql-trunk:

The files sql/lex_hash.h and sql/sql_yacc.h are automatically
generated, and should not be checked in the configuration management system.
These files are now removed.
No changes are required for .bzrignore, which already listed these files
(and similar files in libmysqld/).

The file storage/perfschema/unittest/pfs_timer-t.cc did not build
after the header files refactoring affecting mysql_priv.h
The file now builds properly using sql_priv.h