Avoid warnings about narrowing casts in the long long tests.

Recent g++ versions give -Wnarrowing warning when a value outside of the type
range is used to initialize a variable of this type in { }. Avoid it in the
long long tests using explicit casts as we already cast between long long and
unsigned long long values here anyhow.

tests/strings/strings.cpp

@@ -602,14 +602,16 @@ enum
     Number_Long     = 16    // only for long tests
 };
 
+#ifdef wxLongLong_t
+typedef wxLongLong_t TestValue_t;
+#else
+typedef long TestValue_t;
+#endif
+
 static const struct ToLongData
 {
     const wxChar *str;
-#ifdef wxLongLong_t
-    wxLongLong_t value;
-#else
-    long value;
-#endif // wxLongLong_t
+    TestValue_t value;
     int flags;
     int base;
 
@@ -631,7 +633,7 @@ static const struct ToLongData
 
     { wxT("-1"), -1, Number_Signed | Number_Long },
     // this is surprising but consistent with strtoul() behaviour
-    { wxT("-1"), ULONG_MAX, Number_Unsigned | Number_Long },
+    { wxT("-1"), (TestValue_t)ULONG_MAX, Number_Unsigned | Number_Long },
 
     // this must overflow, even with 64 bit long
     { wxT("922337203685477580711"), 0, Number_Invalid },
@@ -639,8 +641,9 @@ static const struct ToLongData
 #ifdef wxLongLong_t
     { wxT("2147483648"), wxLL(2147483648), Number_LongLong },
     { wxT("-2147483648"), wxLL(-2147483648), Number_LongLong | Number_Signed },
-    { wxT("9223372036854775808"), wxULL(9223372036854775808), Number_LongLong |
-                                                             Number_Unsigned },
+    { wxT("9223372036854775808"),
+      TestValue_t(wxULL(9223372036854775808)),
+      Number_LongLong | Number_Unsigned },
 #endif // wxLongLong_t
 
     // Base tests.