Post-release destabilisation! Completely remove the struct type

'Config' in putty.h, which stores all PuTTY's settings and includes an
arbitrary length limit on every single one of those settings which is
stored in string form. In place of it is 'Conf', an opaque data type
everywhere outside the new file conf.c, which stores a list of (key,
value) pairs in which every key contains an integer identifying a
configuration setting, and for some of those integers the key also
contains extra parts (so that, for instance, CONF_environmt is a
string-to-string mapping). Everywhere that a Config was previously
used, a Conf is now; everywhere there was a Config structure copy,
conf_copy() is called; every lookup, adjustment, load and save
operation on a Config has been rewritten; and there's a mechanism for
serialising a Conf into a binary blob and back for use with Duplicate
Session.

User-visible effects of this change _should_ be minimal, though I
don't doubt I've introduced one or two bugs here and there which will
eventually be found. The _intended_ visible effects of this change are
that all arbitrary limits on configuration strings and lists (e.g.
limit on number of port forwardings) should now disappear; that list
boxes in the configuration will now be displayed in a sorted order
rather than the arbitrary order in which they were added to the list
(since the underlying data structure is now a sorted tree234 rather
than an ad-hoc comma-separated string); and one more specific change,
which is that local and dynamic port forwardings on the same port
number are now mutually exclusive in the configuration (putting 'D' in
the key rather than the value was a mistake in the first place).

One other reorganisation as a result of this is that I've moved all
the dialog.c standard handlers (dlg_stdeditbox_handler and friends)
out into config.c, because I can't really justify calling them generic
any more. When they took a pointer to an arbitrary structure type and
the offset of a field within that structure, they were independent of
whether that structure was a Config or something completely different,
but now they really do expect to talk to a Conf, which can _only_ be
used for PuTTY configuration, so I've renamed them all things like
conf_editbox_handler and moved them out of the nominally independent
dialog-box management module into the PuTTY-specific config.c.

[originally from svn r9214]

Recipe

@@ -245,7 +245,7 @@ CFLAGS += -DWINVER=0x0500 -D_WIN32_WINDOWS=0x0410 -D_WIN32_WINNT=0x0500
 
 # Terminal emulator and its (platform-independent) dependencies.
 TERMINAL = terminal wcwidth ldiscucs logging tree234 minibidi
-         + config dialog
+         + config dialog conf
 
 # GUI front end and terminal emulator (putty, puttytel).
 GUITERM  = TERMINAL window windlg winctrls sizetip winucs winprint
@@ -272,7 +272,7 @@ SFTP     = sftp int64 logging
 
 # Miscellaneous objects appearing in all the network utilities (not
 # Pageant or PuTTYgen).
-MISC     = timing misc version settings tree234 proxy
+MISC     = timing misc version settings tree234 proxy conf
 WINMISC  = MISC winstore winnet winhandl cmdline windefs winmisc winproxy
          + wintime
 UXMISC   = MISC uxstore uxsel uxnet cmdline uxmisc uxproxy time
@@ -315,12 +315,12 @@ psftp    : [C] psftp winsftp wincons WINSSH BE_SSH SFTP wildcard WINMISC
 
 pageant  : [G] winpgnt sshrsa sshpubk sshdes sshbn sshmd5 version tree234
          + misc sshaes sshsha winpgntc sshdss sshsh256 sshsh512 winutils
-         + winmisc winhelp pageant.res LIBS
+         + winmisc winhelp conf pageant.res LIBS
 
 puttygen : [G] winpgen sshrsag sshdssg sshprime sshdes sshbn sshmd5 version
          + sshrand winnoise sshsha winstore misc winctrls sshrsa sshdss winmisc
          + sshpubk sshaes sshsh256 sshsh512 import winutils puttygen.res
-	 + tree234 notiming winhelp winnojmp LIBS wintime
+	 + tree234 notiming winhelp winnojmp conf LIBS wintime
 
 pterm    : [X] GTKTERM uxmisc misc ldisc settings uxpty uxsel BE_NONE uxstore
          + uxsignal CHARSET cmdline uxpterm version time xpmpterm xpmptcfg
@@ -338,7 +338,7 @@ plink    : [U] uxplink uxcons NONSSH UXSSH U_BE_ALL logging UXMISC uxsignal
 puttygen : [U] cmdgen sshrsag sshdssg sshprime sshdes sshbn sshmd5 version
          + sshrand uxnoise sshsha misc sshrsa sshdss uxcons uxstore uxmisc
          + sshpubk sshaes sshsh256 sshsh512 import puttygen.res time tree234
-	 + uxgen notiming
+	 + uxgen notiming conf
 
 pscp     : [U] pscp uxsftp uxcons UXSSH BE_SSH SFTP wildcard UXMISC
 psftp    : [U] psftp uxsftp uxcons UXSSH BE_SSH SFTP wildcard UXMISC