A cheap performance optimization

[Matthias Clasen <mclasen redhat com>]

One of the compiler people here at RedHat complained to me that most of
Gnome is linked with --export-dynamic, which really bloats both the size
and the load times (although prelink may alleviate that a bit). The ld
documentation contains exact details about when --export-dynamic is
needed, but it is never needed for libraries, and in most cases, it is
not needed for apps either. 

Currently, most of Gnome gets --export-dynamic from gmodule-2.0.pc,
which is required by many libraries. Fortunately, with GLib 2.6, fixing
this is as easy as requiring gmodule-no-export-2.0.pc instead of
gmodule-2.0.pc. For completeness, I just added gmodule-export-2.0.pc as
well.

It would be a nice goal for Gnome 2.10 to replace all uses of
gmodule-2.0.pc by either gmodule-no-export-2.0.pc or gmodule-
export-2.0.pc (I guess the latter will be rarely needed).

Regards,

Matthias