Add LENGTH_OF() macro.

Determining the length of arrays that could be calculated at compile time was a bit piecemeal, with special macros used sometimes and with the math done directly other times.

This macro makes the task easier, uses less space, and automatically adjusts when the type changes.

test/src/module/command/verifyTest.c

@@ -23,7 +23,7 @@ testRun(void)
 
     // Install local command handler shim
     static const ProtocolServerHandler testLocalHandlerList[] = {PROTOCOL_SERVER_HANDLER_VERIFY_LIST};
-    hrnProtocolLocalShimInstall(testLocalHandlerList, PROTOCOL_SERVER_HANDLER_LIST_SIZE(testLocalHandlerList));
+    hrnProtocolLocalShimInstall(testLocalHandlerList, LENGTH_OF(testLocalHandlerList));
 
     StringList *argListBase = strLstNew();
     hrnCfgArgRawZ(argListBase, cfgOptStanza, "db");