Merge from petecoup/shortvec-in-struct branch.

Fixes issue #49: using short vector types in struct declarations
would give a bogus parse error.

tests/struct-test-124.ispc

@@ -0,0 +1,15 @@
+
+export uniform int width() { return programCount; }
+
+
+export void f_v(uniform float RET[]) {
+    varying struct { float<2> v; } a;
+    a.v.x = 1;
+    a.v.y = 2;
+    RET[programIndex] = a.v.x + a.v.y;
+}
+
+
+export void result(uniform float RET[]) {
+    RET[programIndex] = 3;
+}

tests/struct-test-125.ispc

@@ -0,0 +1,15 @@
+
+export uniform int width() { return programCount; }
+
+
+export void f_v(uniform float RET[]) {
+    varying struct { float<2> v; } a;
+    a.v[0] = 1;
+    a.v[1] = 2;
+    RET[programIndex] = a.v[0] + a.v[1];
+}
+
+
+export void result(uniform float RET[]) {
+    RET[programIndex] = 3;
+}