crt: gdtoa: Replace atexit by __attribute__((destructor))

This avoid overhead of atexit call which requires dynamic allocation and
for DLL builds also larger code which is statically linked into every DLL.

Signed-off-by: LIU Hao <lh_mouse@126.com>

mingw-w64-crt/gdtoa/misc.c

diff --git a/mingw-w64-crt/gdtoa/misc.c b/mingw-w64-crt/gdtoa/misc.c
index 74a2ca6..960543a 100644
--- a/mingw-w64-crt/gdtoa/misc.c
+++ b/mingw-w64-crt/gdtoa/misc.c
@@ -59,6 +59,8 @@
    2 = initialized
    3 = deleted
 */
+
+__attribute__((destructor))
 static void dtoa_lock_cleanup (void)
 {
 	long last_CS_init = InterlockedExchange (&dtoa_CS_init,3);
@@ -80,7 +82,6 @@
 			int i;
 			for (i = 0; i < NLOCKS;  i++)
 				InitializeCriticalSection (&dtoa_CritSec[i]);
-			atexit (dtoa_lock_cleanup);
 			(void)InterlockedExchange (&dtoa_CS_init, 2);
 		}
 	}