Rename files from main.cpp to more meaningful names.

Because the main file for the dummy-executable and the actual compile
test were both called main.cpp, they were overwriting each other during
in-source builds.

Tests/CompileDefinitions/compiletest.cpp

@@ -0,0 +1,33 @@
+
+#ifndef CMAKE_IS_FUN
+#error Expect CMAKE_IS_FUN definition
+#endif
+
+#if CMAKE_IS != Fun
+#error Expect CMAKE_IS=Fun definition
+#endif
+
+
+template<bool test>
+struct CMakeStaticAssert;
+
+template<>
+struct CMakeStaticAssert<true> {};
+
+static const char fun_string[] = CMAKE_IS_;
+#ifndef NO_SPACES_IN_DEFINE_VALUES
+static const char very_fun_string[] = CMAKE_IS_REALLY;
+#endif
+
+enum {
+  StringLiteralTest1 = sizeof(CMakeStaticAssert<sizeof(CMAKE_IS_) == sizeof("Fun")>)
+#ifndef NO_SPACES_IN_DEFINE_VALUES
+  ,
+  StringLiteralTest2 = sizeof(CMakeStaticAssert<sizeof(CMAKE_IS_REALLY) == sizeof("Very Fun")>)
+#endif
+};
+
+int main(int argc, char **argv)
+{
+  return 0;
+}