json-c: Update to 0.13.1 (#7419)

* json-c: Update to 0.13.1

0.12.1 does not compile with GCC 7.

* json-c: Add patch to make 0.12.1 build with gcc 7

var/spack/repos/builtin/packages/json-c/package.py

@@ -30,9 +30,16 @@ class JsonC(AutotoolsPackage):
     homepage = "https://github.com/json-c/json-c/wiki"
     url      = "https://s3.amazonaws.com/json-c_releases/releases/json-c-0.12.1.tar.gz"
 
+    version('0.13.1', '04969ad59cc37bddd83741a08b98f350')
     version('0.12.1', '55f7853f7d8cf664554ce3fa71bf1c7d')
     version('0.11',   'aa02367d2f7a830bf1e3376f77881e98')
 
     depends_on('autoconf', type='build')
 
     parallel = False
+
+    @when('@0.12.1 %gcc@7')
+    def patch(self):
+        filter_file('-Wextra',
+                    '-Wextra -Wno-error=implicit-fallthrough',
+                    'Makefile.in')