Fix Chromium NaCl build.

Chromium's NaCl build has _POSIX_SOURCE already defined, so #undef it first.
The compiler used also dislikes static asserts with the same name.

Change-Id: I0283fbad1a2ccf98cdb0ca2a7965b15441806308
Reviewed-on: https://boringssl-review.googlesource.com/5430
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/bio/socket_helper.c b/crypto/bio/socket_helper.c
index 481278f..7e677f7 100644
--- a/crypto/bio/socket_helper.c
+++ b/crypto/bio/socket_helper.c
@@ -12,6 +12,7 @@
  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
 
+#undef _POSIX_C_SOURCE
 #define _POSIX_C_SOURCE 200112L
 
 #include <openssl/bio.h>
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index 18d9d4a..0503e13 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -1586,11 +1586,11 @@
 
 OPENSSL_COMPILE_ASSERT(kNumExtensions <=
                            sizeof(((SSL *)NULL)->s3->tmp.extensions.sent) * 8,
-                       too_many_extensions_for_bitset);
+                       too_many_extensions_for_sent_bitset);
 OPENSSL_COMPILE_ASSERT(kNumExtensions <=
                            sizeof(((SSL *)NULL)->s3->tmp.extensions.received) *
                                8,
-                       too_many_extensions_for_bitset);
+                       too_many_extensions_for_received_bitset);
 
 static const struct tls_extension *tls_extension_find(uint32_t *out_index,
                                                       uint16_t value) {