Generate $module-public-headers.txt file, feed it to gtk-doc

Rather than having the gtk-doc build machinery have a list of header
files to exclude, change the GLib build to dump a list of public
header files generated from the maintained Makefile.am files for
each of glib/, gobject/, gio/.

Also, for glib, always install glib-unix.h, even on non-Unix
platforms, for the same reason we install gwin32.h even on Unix.

https://bugzilla.gnome.org/show_bug.cgi?id=651745

docs/reference/glib/Makefile.am

@@ -19,35 +19,9 @@ SCAN_OPTIONS=--deprecated-guards="G_DISABLE_DEPRECATED" --ignore-decorators="GLI
 MKDB_OPTIONS=--sgml-mode --output-format=xml --name-space=g
 
 # Used for dependencies
-HFILE_GLOB=$(top_srcdir)/glib/*.h $(top_srcdir)/gmodule/*.h
+HFILE_GLOB=$(addprefix $(top_srcdir)/glib/,$(shell cat $(top_srcdir)/glib/glib-public-header-files.txt)) $(top_srcdir)/gmodule/*.h
 CFILE_GLOB=$(top_srcdir)/glib/*.c $(top_srcdir)/gmodule/*.c
 
-# Headers to ignore
-IGNORE_HFILES=			\
-	gdatasetprivate.h	\
-	glibintl.h		\
-	gbsearcharray.h		\
-	gmoduleconf.h		\
-	gunibreak.h		\
-	gunicomp.h		\
-	gunidecomp.h		\
-	gunichartables.h	\
-	glib_trace.h		\
-	libcharset.h		\
-	gdebug.h		\
-	gprintfint.h		\
-	gmirroringtable.h	\
-	gscripttable.h		\
-	glib-mirroring-tab	\
-	gnulib			\
-	pcre			\
-	update-pcre		\
-	gbufferprivate.h	\
-	gvariant-internal.h	\
-	gvariant-serialiser.h	\
-	gvariant-core.h		\
-	gvarianttypeinfo.h
-
 # Images to copy into HTML directory
 HTML_IMAGES =  				\
 	file-name-encodings.png		\