package/cairo: update license information

As noticed by Rahul Bedarkar, the cairo library is LGPLv2.1 only
(not LGPLv2.1+) or MPLv1.1.

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 0768932a0229b2c201c292023f59a868ecdb1222)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/cairo/cairo.mk

@@ -6,8 +6,8 @@
 
 CAIRO_VERSION = 1.14.8
 CAIRO_SOURCE = cairo-$(CAIRO_VERSION).tar.xz
-CAIRO_LICENSE = LGPLv2.1+
-CAIRO_LICENSE_FILES = COPYING
+CAIRO_LICENSE = LGPLv2.1 or MPLv1.1 (library)
+CAIRO_LICENSE_FILES = COPYING COPYING-LGPL-2.1 COPYING-MPL-1.1
 CAIRO_SITE = http://cairographics.org/releases
 CAIRO_INSTALL_STAGING = YES
 CAIRO_AUTORECONF = YES