- As a sideeffect of the patch to generate lex_hash.h only once
on the machine where the source dist was produced, a problem
was found when compiling a mysqld without partition support - it 
would crash when looking up the lex symbols due to mismatch between
lex.h and the generated lex_hash.h

 - Remove the ifdef for partition in lex.h 
 - Fix minor problem with"EXPLAIN PARTITION" when not compiled with
   partition(existed also without the above patch)
 - Add test case that will be run when we don't have partition
   support compiled into mysqld
 - Return error ER_FEATURE_DISABLED if user tries to use PARTITION
   when there is no support for it.


sql/lex.h:
  There should be no ifdefs of features in lex.h
sql/sql_class.cc:
  In line with the comment in sql_yacc.yy that we want the same output
  from "EXPLAIN PARTITIONS.." regardless of wheter we have compiled in
  support for partition  or not, remove the ifdef so the extra field
  is added to output if the DESCRIBE_PARTITIONS bit it set. Without
  this patch we get a crash as the code in select_describe believes the
  field is there.
sql/sql_select.cc:
  Use "const" for the variable as it's a ssigned once and never changes
sql/sql_yacc.yy:
  Don't allow PARTITION syntax oif there is no suport for partitioning
mysql-test/r/not_partition.require:
  New BitKeeper file ``mysql-test/r/not_partition.require''
mysql-test/r/not_partition.result:
  New BitKeeper file ``mysql-test/r/not_partition.result''
mysql-test/t/not_partition.test:
  New BitKeeper file ``mysql-test/t/not_partition.test''