This commit updates the libcharset submodule to incorporate the
autotools-ification that I just pushed to that subproject, and builds
on it by replacing Halibut's own makefile system similarly with an
autotools setup.

The new Makefile.am incorporates both of the old Makefile and
doc/Makefile, so a single run of 'make' should now build Halibut
itself and all the formats of its own documentation, which also means
that the automake-generated 'make install' target can do the right
thing in terms of putting an appropriate subset of those documentation
formats in the assorted installation directories.

The old Makefiles are gone, as is release.sh (which is now obsolete
because autotools's 'make dist' doesn't do anything obviously wrong).
The bob build script is comprehensively rewritten, but should still
work - even the clang-based Windows build can use the
autotools-generated makefile system, provided I do the libcharset
build with a manual override of bin_PROGRAMS to prevent it trying to
build the libcharset supporting utilities (which are not completely
Windows-portable).

Thanks to Leah Neukirchen for pointing out that it was left out of
that special-case rule.

Or rather, clang in MS-targeted code generation but still with the
Unix-style command line, which lets me use the existing Makefile with
almost no change.

I became aware a few months ago that enough is known about CHM files
that free software _can_ write them without benefit of the MS HTML
Help compiler - in particular there's a thing called 'chmcmd' in the
Free Pascal Compiler software distribution which is more or less a
drop-in replacement for hhc.exe itself.

But although depending on chmcmd would be a bit nicer than depending
on hhc.exe, Halibut has always preferred to do the whole job itself if
it can. So here's my own from-scratch code to generate CHM directly
from Halibut source.

The new output mode is presented as a completely separate top-level
thing independent of HTML mode. Of course, in reality, the two back
ends share all of the HTML-generation code, differing only in a few
configuration defaults and the minor detail of what will be _done_
with each chunk of HTML as it's generated (this is what the recent
refactoring in b3db1cce3 was in aid of). But even so, the output modes
are properly independent from a user-visible-behaviour perspective:
they use parallel sets of config directives rather than sharing the
same ones (you can set \cfg{html-foo} and \cfg{chm-foo} independently,
for a great many values of 'foo'), and you can run either or neither
or both as you choose in a given run of Halibut.

The old HTML Help support, in the form of some config directives for
HTML mode to output the auxiliary files needed by hhc.exe, is still
around and should still work the same as it always did. I have no real
intention of removing it, partly for the reasons stated in the manual
(someone might find it useful to have Halibut generate the .HHP file
once and then make manual adjustments to it, so that they can change
styling options that the direct CHM output doesn't permit), and mostly
because it wouldn't save a great deal of code or complexity in any
case - the big two of the three auxiliary files (the HHC and HHK) have
to be generated _anyway_ to go inside the .CHM, so all the code would
have to stay around regardless.

The general routines for analysing a buffer into an LZ77ish stream of
literals and matches, and for constructing a Huffman tree in canonical
format, now live in their own source files so that they can be reused
for other similar compression formats. Deflate-specific details like
the exact file encoding are left in deflate.c.

Now you can 'make install prefix=/some/previously/nonexistent/path'
and have all the necessary subdirs created for you.

A long time ago, it seemed like a good idea to arrange that binaries
of Halibut would automatically cease to identify themselves as a
particular upstream version number if any changes were made to the
source code, so that if someone made a local tweak and distributed the
result then I wouldn't get blamed for the results. Since then I've
decided the whole idea is more trouble than it's worth, so I'm
retiring it completely.

[originally from svn r10254]

Watson.)

[originally from svn r8422]

not yet in PDF.  There's a lot of cleaning up to be done, especially in the
area of error, but I think it would be better committed gradually.

[originally from svn r7198]