Experiment: success
Conclusion: no

Various cleanups and simplifications of the makefiles, plus:

- an additional 'make RELEASE_BUILD=1' mode which switches on
  optimisation and -D_FORTIFY_SOURCE=2, and switches off -Werror
- Use RELEASE_BUILD=1 in rpm and deb packaging
- Build with PIE and full RELRO by default
- Add CFLAGS_APPEND to append options instead of overriding CFLAGS

And fix some issues it complains about. Also tweak one issue found by
adding -Wmissing-field-initializers temporarily (that warning is too
fussy to enable by default).

It's a bit stream-of-consciousness at the moment but I hope it will be
useful to help people get started.

Use -MF to make gcc output the autogenerated rules into dotfiles so that
they don't clutter up listings.

I don't believe this stuff is used any more and it's confusing to have a
web/ directory and a webclient/ directory.

When ipc_check() attempts to reconnect it passes ipc_parent as the
target to connect to. ipc_connect() then reconnects and frees ipc_parent
and sets it to strdup(target). When target is equal to ipc_parent this
means we're strduping a freed pointer and reconnecting a second time (or
using ipc_parent anywhere subsequently) will fail. Add a check to make
sure they're not pointing to the same thing.

js.c:17:32: error: option ‘-Winvalid-offsetof’ is valid for C++/ObjC++ but not for C [-Werror=pragmas]
 #pragma GCC diagnostic ignored "-Winvalid-offsetof"
                                ^~~~~~~~~~~~~~~~~~~~
js.c:21:32: error: option ‘-Winvalid-offsetof’ is valid for C++/ObjC++ but not for C [-Werror=pragmas]
 #pragma GCC diagnostic warning "-Winvalid-offsetof"
                                ^~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
../../Makefile.common:104: recipe for target 'js.o' failed

New in gcc 6:

  comms.c: In function ‘json_escape’:
  comms.c:337:8: error: this ‘else’ clause does not guard... [-Werror=misleading-indentation]
         }else
          ^~~~
  comms.c:338:32: note: ...this statement, but the latter is misleadingly
  indented as if it is guarded by the ‘else’
        mws_add(line, "%c", *in); break;
                                  ^~~~~
  cc1: all warnings being treated as errors

with -fpie. Update the credits a little

Needed the server to send an error response instead of immediately
closing, and wait for it to be sent.
also needed certain parts of the client shutdown proceedure tonot
cleanup/free things that hadnt yet been initialised.

Makefile.common uses it to find the mw.rev file