Add rsRand(float, float) support back to compat lib.

Change-Id: I0acaa409908f83c690c95b47979f820bc2dac9f5
diff --git a/cpu_ref/rsCpuRuntimeMath.cpp b/cpu_ref/rsCpuRuntimeMath.cpp
index ee82328..04a80e0 100644
--- a/cpu_ref/rsCpuRuntimeMath.cpp
+++ b/cpu_ref/rsCpuRuntimeMath.cpp
@@ -96,7 +96,7 @@
     m->transpose();
 }
 
-static float SC_randf2(float min, float max) {
+float SC_randf2(float min, float max) {
     float r = (float)rand();
     r /= RAND_MAX;
     r = r * (max - min) + min;