Now the client can use it too if necessary.

Move the bits which specified the default server options and config file
paths out of the config system. Add some bits to simplify constructing an
array of default config options.

Dedupe it into src/user.c where it fits and rewrite it in terms of a new
user_find_name function which will be used more later.

Move it from src/{web,}client/user.[ch] into src/user.c and simplify
with pwrite(2).

Until now configuring mwserv has been limited to command line options
and build configuration. This config system should make things a bit
more flexible by adding the ability to load bits and pieces from a
json config file (or many json config files).

This is how it works:
1. A json object 'cfg' is built containing the build-time defaults for
   each config option recognised by mwserv. This will be used to
   validate the options in config files later.
2. A json config file in the user's home directory is loaded if it
   exists. It does not have to be complete: its contents will be merged
   into the defaults. Unrecognised options are ignored.
3. Otherwise, a config file in /etc is loaded and used similarly.
4. Command line options are parsed and the cfg object is updated with
   cfg_set_* in the order in which the options are found.
   4a. If the [--config|-c <file>] option is encountered, the file is
   loaded and merged into the cfg object as before.
5. Once all of the config information is gathered and merged into the
   cfg object, if the [--print-config|-P] option was given, the final
   merged config is printed in json format (mwserv then exits).
6. Config options are then accessed using the cfg_get_* type-specific
   functions.

This should allow the build system to be simplified in future, e.g.
'make test' could go away in favour of using ~/.mwserv.conf to store
the test environment configuration.

For now, the place to add new config options and their default values is
in cfg_init_defaults() in servercfg.c.

Tip: this can be avoided by adding this to your .vimrc:

match ErrorMsg '\s\+$'

Adding tags to the root .gitignore will make git ignore tags files in
any subdirectory so there's no need for a second .gitignore.

'make test' sets libdir to a path in the test sandbox and it propagates
to the mozjs build if it hasn't been built yet. Reinstate a sensible
libdir for mozjs.

Also disable building libmozjs.so and tidy up the mozjs-related make
rules/variables.

Keeping everything js-related under a mozjs directory simplifies the
build and reduces clutter. This also switches building mozjs in a
separate build directory so that the built files can be more easily
ignored. So we now have:

Source:          mozjs/mozjs17.0.0/
Built files:     mozjs/build/
Installed files: mozjs/installroot/

This also adds the --disable-tests configure option.

improving with a tag and proper version numbers later.

Helps to display the event messages

this moves (most of) the mrod and zod commands to the server

over to the new protocol. Should be tranformed into a request to the
server to perform an action, followed by a response and an announcment
of wether the command succeeded.

thus fixing one major dependancy on the who list

Needs work: message head is currently pid of sender, 
      needs to be userposn of sender instead/aswell

Prep work for persistant/replay messaging; Add serial numbers and datestamps to every message processed by the server, fix timestamp printing to use those values instead of wallclock