Add a few Subzero intrinsics (not the atomic ones yet).

crosstest/mem_intrin.h

Index: crosstest/mem_intrin.h
diff --git a/crosstest/mem_intrin.h b/crosstest/mem_intrin.h
new file mode 100644
index 0000000000000000000000000000000000000000..97e6dccabef0bdf574775f423bd140f2085781c5
--- /dev/null
+++ b/crosstest/mem_intrin.h
@@ -0,0 +1,19 @@
+/*
+ * Simple sanity test of memcpy, memmove, and memset intrinsics.
+ * (fixed length buffers, variable length buffers, etc.).
+ * There is no include guard since this will be included multiple times,
+ * under different namespaces.
+ */
+
+/* Declare first buf as uint8_t * and second as void *, to avoid C++
+ * name mangling's use of substitutions. Otherwise Subzero's name
+ * mangling injection will need to bump each substitution sequence ID
+ * up by one (e.g., from S_ to S0_ and S1_ to S2_).
+ */
+int memcpy_test(uint8_t *buf, void *buf2, uint8_t init, size_t length);
+int memmove_test(uint8_t *buf, void *buf2, uint8_t init, size_t length);
+int memset_test(uint8_t *buf, void *buf2, uint8_t init, size_t length);
+
+int memcpy_test_fixed_len(uint8_t init);
+int memmove_test_fixed_len(uint8_t init);
+int memset_test_fixed_len(uint8_t init);