Add random::get() instead of extern global, which crashes Rack when

used from plugins on Windows.

include/random.hpp

@@ -88,24 +88,26 @@ struct Xoroshiro128Plus {
 
 // Easy random API
 
-extern thread_local Xoroshiro128Plus rng;
-
-
 /** Initializes the thread-local RNG state.
 Must call when creating a thread, otherwise random state is undefined (might always return 0).
 */
 void init();
+
+/** Returns the thread-local generator.
+*/
+Xoroshiro128Plus& get();
+
 /** Returns a uniform random uint64_t from 0 to UINT64_MAX */
 inline uint64_t u64() {
-	return rng.u64();
+	return get().u64();
 }
 /** Returns a uniform random uint32_t from 0 to UINT32_MAX */
 inline uint32_t u32() {
-	return rng.u32();
+	return get().u32();
 }
 /** Returns a uniform random float in the interval [0.0, 1.0) */
 inline float uniform() {
-	return rng.f32();
+	return get().f32();
 }
 /** Returns a normal random number with mean 0 and standard deviation 1 */
 float normal();

src/random.cpp

@@ -30,6 +30,11 @@ void init() {
 }
 
 
+Xoroshiro128Plus& get() {
+	return rng;
+}
+
+
 float normal() {
 	// Box-Muller transform
 	float radius = std::sqrt(-2.f * std::log(1.f - uniform()));