dist/tools: add Coccinelle check for ARRAYSIZE

This Coccinelle script will warn when new code has the potential to use
the macro ARRAYSIZE instead of something like this
     sizeof(some_array) / sizeof(some_array[0])

dist/tools/coccinelle/warn/arraysize.cocci

@@ -0,0 +1,58 @@
+// Use the macro ARRAY_SIZE when possible
+//
+// Confidence: High
+// Copyright: (C) Gilles Muller, Julia Lawall, EMN, INRIA, DIKU.  GPLv2.
+// URL: http://coccinelle.lip6.fr/rules/array.html
+// Options: -I ... -all_includes can give more complete results
+
+// This is a modified version for RIOT-OS.
+// At first it was used to help with Pull Request 11865
+// Now it helps to warn when it is possible to use the macro
+// in new code.
+
+@@
+type T;
+T[] E;
+@@
+
+- (sizeof(E)/sizeof(*E))
++ ARRAY_SIZE(E)
+
+@@
+type T;
+T[] E;
+T E2;
+@@
+
+- (sizeof(E)/sizeof(E2))
++ ARRAY_SIZE(E)
+
+@@
+type T;
+T[] E;
+@@
+
+- (sizeof(E)/sizeof(E[...]))
++ ARRAY_SIZE(E)
+
+@@
+type T;
+T[] E;
+@@
+
+- (sizeof(E)/sizeof(T))
++ ARRAY_SIZE(E)
+
+@n@
+identifier AS,E;
+@@
+
+- #define AS(E) ARRAY_SIZE(E)
+
+@@
+expression E;
+identifier n.AS;
+@@
+
+- AS(E)
++ ARRAY_SIZE(E)