community/w3m: some improvements

Some improvements to the w3m package. Comments (hopefully not too many) in the APKBUILD itself.

Some further observations:

• (some) "CGI" scripts (like dictionary and mailer) were installed even though disabled in the ./configure options, most likely configure disabled the usage of the scripts in the C-compiled binary, but Makefile wasn't updated accordingly. I have tested the scripts, and those that are working have been moved into a -perl subpackage that depends upon perl.

• even though we have --enable-image=fb instead of --enable-image=x11, our imlib2 package depends on libx11, so we end up having x11 dependencies for w3m image support. I have moved that to the -image subpackage, so the parent w3m package can be installed without pulling in x11 libraries. I also added an install_if, so if imlib2 is already installed, you automatically get the -image subpackage when installing w3m; and I removed w3m-image's depends on w3m to allow other packages to use it (I think neofetch and ranger, can do so) without pulling in w3m.

• help files were not installed (or didn't have the correct filename) resulting in the 'H' key binding erroring out. the complete reason for HELP_ALLFILES being there is that w3m supports Lynx keybindings too (will be the default if --enable-keymap=lynx is passed to ./configure, but can still be enabled by copying keymap.lynx in the w3m-doc package to ~/.w3m/keymap), and without specifying which help files to install, the help files for those keybindings were installed too.

Lastly, I hope including w3mhelp-w3m_ja.html is okay, because there is a hyperlink to that from w3mhelp-w3m_en.html (at the very top of that page). In order to not have a "Can't load w3mhelp-w3m_ja.html" error upon clicking that link, the _ja help file has to be included, or the link patched out. I hope the former solution is accepted :-)

If we do not use --disable-help-cgi then the locale-specific help files can be generated on the fly, but that would add perl as a dependency.