replace user online check offered to scripts

Use ftruncate instead of writing malloced garbage entries to set the
file size of folders.bb, which dictates the (seemingly arbitrary) 64
folder limit. Also make it return on error instead of exiting.

As we're determined to use git for providing version numbers we might as
well do it the right way. Take all of the version information from git
describe. This assumes that at least one annotated tag exists in the
branch relating to a release. The tag will be created using

$ git tag -a -m "Version 2.17" 2.17 fb1be771

so git describe will give us versions like 2.17-123-gf00baa which has
better ordering properties than the current 2.17-gf00baa scheme, which
is important for package upgrades. When HEAD matches the tag exactly, it
will just give 2.17

Now that !tell is gone it's not needed.

In main(), login_ok() was being called before ipc_connect() but when a
new user is created, the login_ok() call leads to a broadcast() call
which attempts to reconnect to the server through ipc_check() and fails
because ipc_connect() hasn't set the server location yet. This bug has
been lurking for a while but it has only recently turned into a segfault
due to the NULL server location. Move the broadcast() calls to come
after the ipc_connect() for now.

as they should all count as being "user action" messages
fixes #11

as thats where the autoexec stuff gets run. actually fixes #9

this removes the anachronistic single-user wiz command and fixes #8

incoming message pipe. added a quick call to idle to give it a chance. fixes #9

Introduced in commit b5193749. Fixes #7.

Using 0 made it look like all the messages were from the user at offset
0 with spy turned on.

That coccinelle script works better without the semicolons (duh):

@rule0@
expression A,B;
@@
- lseek(A, B, 0)
+ lseek(A, B, SEEK_SET)
@rule1@
expression A,B;
@@
- lseek(A, B, 1)
+ lseek(A, B, SEEK_CUR)
@rule2@
expression A,B;
@@
- lseek(A, B, 2)
+ lseek(A, B, SEEK_END)

Change scripted with coccinelle:

@rule0@
expression A,B;
@@
- lseek(A, B, 0);
+ lseek(A, B, SEEK_SET);
@rule1@
expression A,B;
@@
- lseek(A, B, 1);
+ lseek(A, B, SEEK_CUR);
@rule2@
expression A,B;
@@
- lseek(A, B, 2);
+ lseek(A, B, SEEK_END);

Also get rid of some unnecessary global variables.

sed does it better.

Half of it relates to MUD mode, the other half is out of date.

Spotted by scan-build

Also make the alias type not-a-pointer to improve readability and
allocate all of the memory required for an alias in one go.

Makes sure we don't create the directories with root ownership.

Also make mwserv's stdout line buffered to work better with logging
systems which capture stdout.

- Run as mw:mw
- Make systemd create and cleanup /var/run/mw for us
- Correct the path to mwserv

(And less shouty.)

Make it static but add a convenience pointer to it to take the place of
the previous user pointer. Make the pointer itself const so that the
compiler complains if anything besides the original user's address is
assigned to it.

And tidy up command.c a bit

Don't start at the beginning of the user db each time.