Core: fixed build on Tru64 UNIX.

There was a typo in NGX_EACCES.

Reported by Goetz T. Fischer.

src/core/ngx_shmtx.c

diff --git a/src/core/ngx_shmtx.c b/src/core/ngx_shmtx.c
index 6230dc0..a255903 100644
--- a/src/core/ngx_shmtx.c
+++ b/src/core/ngx_shmtx.c
@@ -259,7 +259,7 @@
 
 #if __osf__ /* Tru64 UNIX */
 
-    if (err == NGX_EACCESS) {
+    if (err == NGX_EACCES) {
         return 0;
     }