Introduce the notion of function addresses in Subzero.

crosstest/test_global_main.cpp

Index: crosstest/test_global_main.cpp
diff --git a/crosstest/test_global_main.cpp b/crosstest/test_global_main.cpp
index 43f96099f44e06a15c65ab881b3f92fbf6db287a..bcaaa7d0d14e36db2323049cf0717c86fe64dad1 100644
--- a/crosstest/test_global_main.cpp
+++ b/crosstest/test_global_main.cpp
@@ -23,6 +23,16 @@ namespace Subzero_ {
 #include "test_global.h"
 }
 
+int ExternName1 = 36363;
+float ExternName2 = 357.05e-10;
+char ExternName3[] = {'a', 'b', 'c'};
+struct {
+  int a;
+  float b;
+  double d;
+} ExternName4 = {-111, 2.69, 55.19};
+double ExternName5 = 3.44e26;
+
 int main(int argc, char **argv) {
   size_t TotalTests = 0;
   size_t Passes = 0;