[gobject-introspection] build: actually require libffi >= 3.0.0

[Colin Walters <walters src gnome org>]

commit e67a2068e208b6c4ceabdd791e58b96030e42001
Author: Dieter Verfaillie <dieterv optionexplicit be>
Date:   Thu May 2 17:12:09 2013 +0200

    build: actually require libffi >= 3.0.0
    
    as documented in README...

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index a73b860..d85a131 100644
--- a/configure.ac
+++ b/configure.ac
@@ -167,7 +167,7 @@ AC_SUBST(CAIRO_GIR_PACKAGE)
 PKG_CHECK_MODULES(SCANNER, [gobject-2.0 gio-2.0])
 
 dnl libffi
-PKG_CHECK_MODULES(FFI, libffi, have_ffi_pkgconfig=yes, have_ffi_pkgconfig=no)
+PKG_CHECK_MODULES(FFI, [libffi >= 3.0.0 ], have_ffi_pkgconfig=yes, have_ffi_pkgconfig=no)
 FFI_PC_CFLAGS=""
 FFI_PC_LIBS=""
 FFI_PC_PACKAGES=""