* glib/Global.cs: Add a public constant field specifying the
calling convention used by GLib and depending libraries.
By now it's hardcoded to Cdecl as every non-Win32 runtime
should ignore this attribute.
* *.cs, *.custom: Use GLib.Global.CallingConvention for both
pinvokes and callbacks. Plugs a stack leak on Win32. All
pinvokes defaulted to StdCall and thus the stack was never
cleaned up.
svn path=/trunk/gtk-sharp/; revision=141175