Be explicit about corner cases for llFrand.

inf and nan already did the right thing in Python, but just in case that doesn't happen in all platforms, we handle them explicitly. Also, that will make it more immune to bugs in future.

lslopt/lslbasefuncs.py

@@ -1058,6 +1058,11 @@ if lslcommon.IsCalc:
     import random
     def llFrand(lim):
         assert isfloat(lim)
+        if math.isinf(lim):
+            return 0.
+        if math.isnan(lim):
+            return lim
+
         lim = F32(lim) # apply constraints
         val = random.random() * lim
         # Truncate, rather than rounding