Fix VL_RANDom to better randomize bits.

Changes

@@ -7,6 +7,8 @@ indicates the contributor was also the author of the fix; Thanks!
 
 **** Fix compile issues with GCC 4.3, bug47.  [Lane Brooks]
 
+**** Fix VL_RANDom to better randomize bits.  [Art Stamness]
+
 * Verilator 3.700 2009/01/08
 
 **   Add limited support for tristate inouts.  Written by Lane Brooks.

bin/verilator

@@ -633,6 +633,12 @@ will call a function to determine the value, this allows randomization of
 all Xs to find reset bugs and is the slowest, but safest for finding reset
 bugs in code.
 
+If using -x-assign unique, you may want to seed your random number
+generator such that each regression run gets a different randomization
+sequence.  Use the system's srand48() or for Windows srand() function to do
+this.  You'll probably also want to print any seeds selected, and code to
+enable rerunning with that same seed so you can reproduce bugs.
+
 =back
 
 =head1 VERILOG ARGUMENTS

include/verilated.cpp

@@ -73,9 +73,9 @@ void vl_fatal (const char* filename, int linenum, const char* hier, const char*
 IData VL_RAND32() {
 #if defined(_WIN32) && !defined(__CYGWIN__)
     // Windows doesn't have lrand48(), although Cygwin does.
-    return (rand()<<16) | rand();
+    return (rand()<<16) ^ rand();
 #else
-    return (lrand48()<<16) | lrand48();
+    return (lrand48()<<16) ^ lrand48();
 #endif
 }