Commands/ directory reorganisation

Dear all,

Patch attached in line with my previous statement on -hackers about
reorganisation of files in the commands directory. (Note that define.c
has been kept, holding some of the common support code for define
routines.)

I have checked this and it compiles and passes regression tests. It is
just straightforward moving of code from one place to another.

I will have to be out until ~1700 UTC Monday -at which point I will be
happy to answer any questions which arise.

Regards

John

Notes to Committer
------------------

The following files are removed in this patch:

src/backend/commands/command.c
src/backend/commands/creatinh.c
src/backend/commands/remove.c
src/backend/commands/rename.c
src/include/commands/command.h
src/include/commands/creatinh.h
src/include/commands/rename.h

The following files are added:

src/backend/commands/aggregatecmds.c
src/backend/commands/domaincmds.c
src/backend/commands/functioncmds.c
src/backend/commands/lockcmds.c
src/backend/commands/operatorcmds.c
src/backend/commands/portalcmds.c
src/backend/commands/schemacmds.c
src/backend/commands/tablecmds.c
src/backend/commands/typecmds.c

src/include/commands/lockcmds.h
src/include/commands/portalcmds.h
src/include/commands/schemacmds.h
src/include/commands/tablecmds.h

Details for commit message:

The contents of command.c, creatinh.c, define.c, remove.c and rename.c
have been divided according to the type of object manipulated -so ALTER
TABLE code is in tablecmds.c, aggregate commands in aggregatecmds.c and
so on.

A few support routines remain in define.c (prototypes in
src/include/commands/defrem.h

No code has been changed except for includes to reflect the new files.
The prototypes for aggregatecmds.c, domaincmds.c, functioncmds.c,
operatorcmds.c, and typecmds.c remain in src/include/commands/defrem.h