Detect CUPS ≥ 1.7

We support CUPS ≥ 1.2, but we use API that was introduced and deprecated
at a later point.

config.h.meson

@@ -26,6 +26,9 @@
 /* Define to 1 if CUPS 1.6 API is available */
 #mesondefine HAVE_CUPS_API_1_6
 
+/* Define to 1 if CUPS 2.0 API is available */
+#mesondefine HAVE_CUPS_API_2_0
+
 /* Define if the GNU dcgettext() function is already present or preinstalled.
    */
 #mesondefine HAVE_DCGETTEXT

modules/printbackends/meson.build

@@ -78,6 +78,9 @@ if enabled_print_backends.contains('cups')
       if cups_major_version > 1 or cups_minor_version >= 6
         cdata.set('HAVE_CUPS_API_1_6', 1)
       endif
+      if cups_major_version > 1 or cups_minor_version >= 7
+        cdata.set('HAVE_CUPS_API_2_0', 1)
+      endif
 
       if cc.compiles('#include <cups/http.h> \n http_t http; char *s = http.authstring;')
         cdata.set('HAVE_HTTP_AUTHSTRING', 1,