ENH: Improve fallback seeding on Windows

Use QueryPerformanceCounter to improve fallback entropy when more than 1 value is needed
Add random_entropy to module import

Author: Sheppard, Kevin

randomstate/__init__.py

@@ -1,4 +1,5 @@
 from __future__ import division, absolute_import, print_function
 
 from randomstate.prng.mt19937 import *
+from randomstate.entropy import random_entropy
 import randomstate.prng

randomstate/src/common/entropy.c

@@ -142,9 +142,14 @@ uint32_t entropy_randombytes(void) {
     gettimeofday(&tv, NULL);
     return entropy_hash_32(getpid()) ^ entropy_hash_32(tv.tv_sec) ^ entropy_hash_32(tv.tv_usec) ^ entropy_hash_32(clock());
 #else
+    uint32_t out = 0;
+    int64_t counter;
     struct _timeb  tv;
     _ftime(&tv);
-    return entropy_hash_32(GetCurrentProcessId()) ^ entropy_hash_32((uint32_t)tv.time) ^ entropy_hash_32(tv.millitm) ^ entropy_hash_32(clock());
+    out = entropy_hash_32(GetCurrentProcessId()) ^ entropy_hash_32((uint32_t)tv.time) ^ entropy_hash_32(tv.millitm) ^ entropy_hash_32(clock());
+    if (QueryPerformanceCounter((LARGE_INTEGER *)&counter) != 0)
+        out ^= entropy_hash_32((uint32_t)(counter & 0xffffffff));
+    return out;
 #endif
 }