devel/glib20: rename DOCS into GTKDOC and disable it by default

Follow the path done for ports depending on doxygen with gtkdoc.
This reduced the number of build dependencies and respects the defaults
of the upstream build system.

Make a GTKDOC option generic so other ports can follow the same path

Mk/bsd.options.desc.mk

@@ -151,6 +151,7 @@ GSTREAMER_DESC?=	Multimedia support via GStreamer
 GTA_DESC?=		Generic Tagged Array (GTA) support
 GTK2_DESC?=		GTK+ 2 GUI toolkit support
 GTK3_DESC?=		GTK+ 3 GUI toolkit support
+GTKDOC_DESC?=		Build Developement Documentation with gtkdoc
 GUI_DESC?=		GUI (Graphical User Interface) support
 GUILE_DESC?=		Guile extension language support
 GVFS_DESC?=		Virtual filesystems support via GVFS

devel/glib20/Makefile

@@ -1,5 +1,6 @@
 PORTNAME=	glib
 DISTVERSION=	2.74.3
+PORTREVISION=	1
 PORTEPOCH=	2
 CATEGORIES=	devel
 MASTER_SITES=	GNOME
@@ -38,13 +39,13 @@ CONFLICTS_INSTALL=	p5-Giovanni
 _LIBVERSION=	0.7400.3
 PLIST_SUB=	LIBVERSION=${_LIBVERSION}
 
-OPTIONS_DEFINE=		DEBUG DOCS FAM_ALTBACKEND MANPAGES NLS TEST
+OPTIONS_DEFINE=		DEBUG GTKDOC FAM_ALTBACKEND MANPAGES NLS TEST
 OPTIONS_DEFAULT=	MANPAGES
 OPTIONS_SUB=		yes
 
-DOCS_BUILD_DEPENDS=	gtk-doc>0:textproc/gtk-doc
-DOCS_IMPLIES=		TEST
-DOCS_MESON_TRUE=	gtk_doc
+GTKDOC_BUILD_DEPENDS=	gtk-doc>0:textproc/gtk-doc
+GTKDOC_IMPLIES=		TEST
+GTKDOC_MESON_TRUE=	gtk_doc
 
 FAM_ALTBACKEND_DESC=	Alternate file monitor backend