Use _POSIX_C_SOURCE not _BSD_SOURCE.

_BSD_SOURCE has been deprecated (see bug). The manpage for printf
suggests that any _POSIX_C_SOURCE >= 200112L is also sufficient to bring
in the needed declarations and the bug reporter confirms that it's
sufficient for him.

https://code.google.com/p/chromium/issues/detail?id=419859

Change-Id: Ifc053f11c5aa1df35aae8e952d2c73a7f4599ec2
Reviewed-on: https://boringssl-review.googlesource.com/1890
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/time_support.c b/crypto/time_support.c
index 5b300b3..4537e82 100644
--- a/crypto/time_support.c
+++ b/crypto/time_support.c
@@ -55,9 +55,7 @@
  * (eay@cryptsoft.com).  This product includes software written by Tim
  * Hudson (tjh@cryptsoft.com). */
 
-#if !defined(_BSD_SOURCE)
-#define _BSD_SOURCE /* for gmtime_r */
-#endif
+#define _POSIX_C_SOURCE 201410L  /* for gmtime_r */
 
 #include <openssl/time_support.h>