Add noreturn declaration compatible with the MSVC compiler.

MSVC provides a compiler declaration to declare that a function
never returns. This declaration is required in front of the
function definition rather than at the end, but fortunately gcc
is compatible with this location as well.

Explicit returns are no longer required after calls to test_die.

Signed-off-by: Julio Espinoza-Sokal <julioes@gmail.com>
Signed-off-by: Andreas Ericsson <ae@op5.se>

tests/t0020-dirent.c

@@ -105,7 +105,6 @@ static int one_entry(void *state, char *path)
 		}
 	}
 	test_die("unexpected path \"%s\"", path);
-	return -1;
 }
 
 
@@ -189,7 +188,6 @@ static walk_data empty = {
 static int dont_call_me(void *state, char *path)
 {
 	test_die("dont_call_me: unexpected callback!");
-	return -1;
 }
 
 BEGIN_TEST(empty)

tests/test_lib.h

@@ -29,6 +29,8 @@
 /** Declare a function never returns to the caller. */
 #ifdef __GNUC__
 # define NORETURN __attribute__((__noreturn__))
+#elif defined(_MSC_VER)
+# define NORETURN __declspec(noreturn)
 #else
 # define NORETURN /* noreturn */
 #endif
@@ -61,8 +63,7 @@ extern void test_end(void);
  *
  * @param fmt printf style format string.
  */
-extern void test_die(const char *fmt, ...)
-	NORETURN
+extern void NORETURN test_die(const char *fmt, ...)
 	GIT_FORMAT_PRINTF(1, 2);
 
 /**