0.4.2: cleanup release

Version 0.4.2 is largely a cleanup release. Changes are minor:

 * Programatically replace libcrypto's random number generator with our
   own (using /dev/urandom or Windows CAPI) since libcrypto's RNG likes
   to use uninitialized memory as one of its entropy sources. This causes
   massive floods of valgrind (debugger) errors during memory error
   profiling analysis.

 * Clean up some other code to eliminate valgrind errors.

Valgrind now runs on Linux with only one error. This error is in
EthernetTap and is a false positive.

version.h

@@ -41,6 +41,6 @@
 /**
  * Revision: 16-bit (0-65535)
  */
-#define ZEROTIER_ONE_VERSION_REVISION 1
+#define ZEROTIER_ONE_VERSION_REVISION 2
 
 #endif