Type convert arrays in select expressions to pointers to the first element.

Fixes issue #345.

tests/select-array-ptr-typeconv.ispc

@@ -0,0 +1,18 @@
+
+uniform float a[1234];
+
+float * uniform func(uniform bool x) {
+    return x ? a : NULL;
+}
+
+export uniform int width() { return programCount; }
+
+export void f_f(uniform float RET[], uniform float aFOO[]) {
+    a[programIndex] = aFOO[programIndex];
+    float * uniform ptr = func(aFOO[0] == 1);
+    RET[programIndex] = ptr[programIndex]; 
+}
+
+export void result(uniform float RET[]) {
+    RET[programIndex] = 1 + programIndex;
+}