serf: fix universal build

Fixes #23342.
Add OS.mac? and OS.linux?
Rename MacOS to OS::Mac
Move MacOS modules under OS::Mac namespace

Closes #23138.
Merge XQuartz and X11 modules
Make condition clearer using names
Extract repeated conditional to a method
Improve superenv add/remove message.

* Now it includes all flags that are added or removed by superenv when
  passing "--verbose" or envvar VERBOSE or HOMEBREW_VERBOSE is set.
libuv 0.10.18

Closes #23353.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
kawa 1.14

Closes #23352.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
lightning 2.0.1

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
lightning: clean up configure flags
node 0.10.21
gobject-introspection: remove unrecognized configure switch
gobject-introspection: override GOBJECT_INTROSPECTION_LIBDIR

Signed-off-by: Kieran Ramos <ramos.kieran@gmail.com>
Signed-off-by: Jack Nagel <jacknagel@gmail.com>
pango: enable gobject-introspection

Closes #23247.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
atk: enable gobject-introspection

Closes #23248.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
gdk-pixbuf: enable gobject-introspection

Closes #23249.

Signed-off-by: Kieran Ramos <ramos.kieran@gmail.com>
Signed-off-by: Jack Nagel <jacknagel@gmail.com>
gtk+3: enable gobject-introspection

Closes #23250.
gobject-introspection: add option to run tests

cf. #22314.