Apply an MSVC compilation fix from Gisle Vanem

This fixes a double-define introduced in 28538069b2f1909a7600ec6d

changes/test.h_msvc

@@ -0,0 +1,3 @@
+  o Minor bugfixes (compilation):
+    - Fix compilation of test.h with MSVC. Patch from Gisle Vanem;
+      bugfix on 0.2.5.5-alpha.

src/test/test.h

@@ -61,7 +61,7 @@
 
 #ifdef _MSC_VER
 #define U64_PRINTF_TYPE uint64_t
-#define U64_PRINTF_TYPE int64_t
+#define I64_PRINTF_TYPE int64_t
 #else
 #define U64_PRINTF_TYPE unsigned long long
 #define I64_PRINTF_TYPE long long