Consequently, rename HAVE_purify to HAVE_valgrind, and related changes.
Leave some comments about purify when not clear that they apply also to Valgrind.
Fix redundant IF_VALGRIND declaration.

Misc. small fixes:
 - Fixes for pool-of-threads patch.
 - Fixes for push of PBXT storage engine.
 - mysql-test-run.pl fix.
 - Fix build problem in compile-pentium64-max.


BUILD/SETUP.sh:
  Rename purify -> valgrind.
BUILD/build_mccge.sh:
  Rename purify -> valgrind.
BUILD/compile-dist:
  Fix that PBXT was missing in source tarball after `BUILD/compile-dist && make dist`
BUILD/compile-pentium64-max:
  Fix a build problem with BUILD/compile-pentium64-max on CentOS/Fedora Core 10 amd64.
        
  On these systems, there is libz.so but no libz.a. Finding libz.so, ./configure decides
  to use system zlib. But since BUILD/compile-pentium64-max builds a fully static binary
  with -all-static, the link of mysqld fails due to missing libz.a.
        
  Fix by using bundled zlib in the build script.
BUILD/compile-solaris-sparc-purify:
  Rename purify -> valgrind.
include/m_string.h:
  Rename purify -> valgrind.
include/my_global.h:
  Rename purify -> valgrind.
mysql-test/Makefile.am:
  Fix that PBXT test suite was missing from `make dist` source tarball.
mysql-test/lib/mtr_unique.pm:
  Better fix to avoid races when chmod'ing the semaphore file.
  (Though using chmod 666 shared files in /tmp/ is still not a very good solution).
mysql-test/t/pool_of_threads.cnf:
  Fix that test case pool_of_threads fails if run on mysqld with no --with-libevent support.
mysys/mf_qsort.c:
  Rename purify -> valgrind.
mysys/my_alloc.c:
  Rename purify -> valgrind.
mysys/my_init.c:
  Rename purify -> valgrind.
mysys/my_rnd.c:
  Rename purify -> valgrind.
mysys/safemalloc.c:
  Rename purify -> valgrind.
scripts/mysql_config.pl.in:
  Rename purify -> valgrind.
scripts/mysql_config.sh:
  Rename purify -> valgrind.
sql/field_conv.cc:
  Rename purify -> valgrind.
sql/filesort.cc:
  Rename purify -> valgrind.
sql/ha_partition.cc:
  Rename purify -> valgrind.
sql/hostname.cc:
  Rename purify -> valgrind.
sql/item_timefunc.cc:
  Rename purify -> valgrind.
sql/log_event.cc:
  Rename purify -> valgrind.
sql/log_event_old.cc:
  Rename purify -> valgrind.
sql/my_decimal.h:
  Rename purify -> valgrind.
sql/mysqld.cc:
  Rename purify -> valgrind.
  Fix redundant IF_VALGRIND declaration.
sql/opt_range.cc:
  Rename purify -> valgrind.
sql/opt_range.h:
  Rename purify -> valgrind.
sql/records.cc:
  Rename purify -> valgrind.
sql/rpl_rli.cc:
  Rename purify -> valgrind.
sql/rpl_rli.h:
  Rename purify -> valgrind.
sql/set_var.cc:
  Fix missing static declaration on pool_of_threads.
sql/slave.cc:
  Rename purify -> valgrind.
sql/sql_base.cc:
  Rename purify -> valgrind.
sql/sql_binlog.cc:
  Rename purify -> valgrind.
sql/sql_class.cc:
  Rename purify -> valgrind.
sql/sql_list.h:
  Rename purify -> valgrind.
sql/sql_load.cc:
  Rename purify -> valgrind.
sql/sql_select.cc:
  Rename purify -> valgrind.
sql/table.cc:
  Rename purify -> valgrind.
storage/archive/azio.c:
  Rename purify -> valgrind.
storage/innobase/buf/buf0buf.c:
  Rename purify -> valgrind.
storage/innobase/include/univ.i:
  Rename purify -> valgrind.
storage/innobase/srv/srv0start.c:
  Rename purify -> valgrind.
storage/maria/ha_maria.cc:
  Rename purify -> valgrind.
storage/maria/ma_blockrec.c:
  Rename purify -> valgrind.
storage/maria/ma_check.c:
  Rename purify -> valgrind.
storage/maria/ma_loghandler.c:
  Rename purify -> valgrind.
storage/maria/ma_packrec.c:
  Rename purify -> valgrind.
storage/maria/ma_page.c:
  Rename purify -> valgrind.
storage/maria/ma_pagecrc.c:
  Rename purify -> valgrind.
storage/maria/ma_search.c:
  Rename purify -> valgrind.
storage/myisam/mi_check.c:
  Rename purify -> valgrind.
storage/myisam/mi_page.c:
  Rename purify -> valgrind.
storage/myisam/mi_search.c:
  Rename purify -> valgrind.
storage/myisammrg/ha_myisammrg.cc:
  Rename purify -> valgrind.
strings/bcmp.c:
  Rename purify -> valgrind.
strings/decimal.c:
  Rename purify -> valgrind.
strings/strmake.c:
  Rename purify -> valgrind.