It is an odd binding that conflicts with typical behavior
where shift click selects multiple items and there is
already the middle click shortcut to close tabs quickly.

Closes #918

This was accidentally left behind, expose it beind an option as
with the old build system but default to false now. Enough time
has passed and only distros that care about it can enable it.

With the switch to meson, the problem previously fixed in #1822 came
back. The build system might pick up the installed hexchat-config.h
instead of using the header in the source directory, as the compiler
arguments would be in the order of "-I${prefix}/include -I..".

It seems that the c_args in meson are always put to the front of the
compiler arguments, in order to be able to override any include paths
from dependencies. However, this was not the intention here, so perl
should also be modeled as a dependency. This ensures that the arguments
with local include directories come first.

The switch to the meson build system broke plugins on macOS. GNU libtool
builds shared libraries with ".dylib" and shared modules (plugins) with
the extension ".so", but meson is using ".dylib" for both.

Although overriding the name_suffix for shared_module() in meson is
possible, this would be messy for other platforms as there is no way to
query the default. Therefore it seems like we have to go with ".dylib"
for now on macOS.

However, G_MODULE_SUFFIX is defined to ".so", because glib follows what
GNU libtool does. Therefore define a separate preprocessor macro that
has the correct extension.

See: mesonbuild/meson#1160

Closes #2186
Closes #1550

This is mostly useful to avoid a newer gettext dependency
for translating the appdata file but it is also just useless
data for some distros without any app store.

Closes #2219