Subzero: Fix and clean up some cross tests.

crosstest/vectors.h

Index: crosstest/vectors.h
diff --git a/crosstest/vectors.h b/crosstest/vectors.h
index 9924eb504f7237de018269f8e056c4f92c3ac5e2..2fdb482868cff246d37cbf8491886312b14e3cb0 100644
--- a/crosstest/vectors.h
+++ b/crosstest/vectors.h
@@ -20,6 +20,13 @@
 #include <string>
 #include <sstream>
 
+// The driver and the test program may be compiled by different
+// versions of clang, with different standard libraries that have
+// different definitions of int8_t.  Specifically, int8_t may be
+// typedef'd as either 'char' or 'signed char', which mangle to
+// different strings.  Avoid int8_t and use an explicit myint8_t.
+typedef signed char myint8_t;
+
 #include "vectors.def"
 
 // PNaCl portable vector types