Fix after manual merge

  Improved concurrency for key cache reassignment

into teton.kitebird.com:/home/paul/mysql-4.1

into deer.(none):/home/hf/work/mysql-4.1.stmt

there was an error about sendind prepared parameters to the server

  Stupid typo. Led to compilation failure with non-gcc compilers.

handling of init-file option added to embedded library
main problem was killing of output (resulting recordsets etc)
i added checks for empty output in Protocol:: methods
better solution could be special Protocol_nul class to redirect
results to nowhere

I made libmysqld not to do freopen(stdout...)
I think we need better solution here so i added it as a worklog entry #1247

into deer.(none):/home/hf/work/mysql-4.1.stmt

into eagle.mysql.r18.ru:/home/vva/work/help_correction/mysql-4.1

into eagle.mysql.r18.ru:/home/vva/work/help_correction/mysql-4.1

embedded library
some fixes - cleanup procedure changed for embedded library - deletion of
embedded mysql->thd

WL604 Privilegies in embedded library
another bug fixed

into deer.(none):/home/hf/work/mysql-4.1.stmt

WL#604 Privileges in embedded library
bugs fixed

into mysql.com:/space/my/mysql-4.1

   if a variable is not defined (empty).

   (crc32.c is included by mysys/my_crc32.c)

into mysql.com:/home/mysql_src/mysql-4.1

Don't free the client's selected db (thd->db) when it has been DROPped,
if this is a slave thread; the x_free() was causing a lot
of various bugs in rpl_loaddata_rule_m (garbage characters, segfault, hangs in
other threads).
A small post-merge fix (rli->inside_transaction exists in 4.0 only).

into mysql.com:/home/dlenev/src/mysql-4.1-rplunt

WL#604 Privileges in embedded library
code added to check privileges in embedded library
NO_EMBEDDED_ACCESS_CHECKS macros inserted in code so we can exclude
access-checking parts. Actually we now can exclude these parts from
standalone server as well. Do we need it?
Access checks are disabled in embedded server by default. One should
edit libmysqld/Makefile manually to get this working.
We definitely need the separate configure for embedded server

- offset of substr begining
- offset of substr end
- number of characters (MB compatible)

null_string wasn't known in libmysqld/lib_sql.cc, that caused compiler's error
i put the declaration of the null_string in mysql_priv.h and renamed it
to my_null_string to reduce the probability of name's intersections

into mishka.mysql.fi:/home/my/mysql-4.1

Now it can work with any character set.

into narttu.mysql.fi:/my/mysql-4.1

   .c files (the IBM Visual Age C compiler aborts with a syntax error
   on these)

   (instead of libedit, which is the default for 4.1)
 - brushed up the usage help text a bit