Version information

[Matthias Clasen <maclas gmx de>]

Hi all, 

I'd like to see information about when an interface was added. My first
attempt was to add this information to the $MODULE-sections.txt file,
like the following example: 

<TITLE>Module Interface</TITLE>
<FILE>module_interface</FILE>
gdk_pixbuf_set_option
gdk_pixbuf_get_formats            2.1.0
gdk_pixbuf_format_get_name        2.1.0
gdk_pixbuf_format_get_description 2.1.0
gdk_pixbuf_format_get_mime_types  2.1.0
gdk_pixbuf_format_get_extensions  2.1.0
gdk_pixbuf_format_is_writable     2.1.0
GdkPixbufFormat                   2.1.0
GdkPixbufFormatFlags              2.1.0
GdkPixbufModulePattern            2.1.0
GdkPixbufModuleFillVtableFunc     
GdkPixbufModuleFillInfoFunc       2.1.0
GdkPixbufModuleSizeFunc           2.1.0
GdkPixbufModulePreparedFunc
GdkPixbufModuleUpdatedFunc
GdkPixbufModule

With the patch attached to #93591, gtk-doc will use this information to
emit "Since: 2.1.0" for the corresponding symbols. (Without the patch
gtk-doc will happily ignore the version info, as I've just verified) 

Does this look like an OK addition ? Do you think we also need to
support version information in the doc comments (like the javadoc @since
tag) ?

Matthias