Add support for "new" and "delete" to the language.

Issue #139.

tests/new-delete-1.ispc

@@ -0,0 +1,15 @@
+
+export uniform int width() { return programCount; }
+
+export void f_fu(uniform float RET[], uniform float aFOO[], uniform float b) {
+    float a = aFOO[programIndex]; 
+    float * uniform buf = uniform new float[programCount];
+    for (uniform int i = 0; i < programCount; ++i)
+        buf[i] = i;
+    RET[programIndex] = buf[a-1];
+    delete buf;
+}
+
+export void result(uniform float RET[]) {
+    RET[programIndex] = programIndex;
+}