Add G_GNUC_BEGIN/END_IGNORE_DEPRECATIONS

Add G_GNUC_BEGIN/END_IGNORE_DEPRECATIONS

Add new macros to disable -Wdeprecated-declarations around a piece of
code, using the C99 (and GNU89) _Pragma() operator. Replace the
existing use of #pragma for this in gio, and suppress the warnings in
gvaluearray.c as well.

https://bugzilla.gnome.org/show_bug.cgi?id=669671