Update NSPR to 4.12 and NSS to 3.23 on iOS

nspr/pr/include/prenv.h

Index: nspr/pr/include/prenv.h
diff --git a/nspr/pr/include/prenv.h b/nspr/pr/include/prenv.h
index 2a4771673a68dbe6745433da852609a7f0a432f4..468c7d596295e7296cff555e04e3351d747d53dc 100644
--- a/nspr/pr/include/prenv.h
+++ b/nspr/pr/include/prenv.h
@@ -91,6 +91,20 @@ PR_BEGIN_EXTERN_C
 NSPR_API(char*) PR_GetEnv(const char *var);
 
 /*
+** PR_GetEnvSecure() -- get a security-sensitive environment variable
+**
+** Description:
+**
+** PR_GetEnvSecure() is similar to PR_GetEnv(), but it returns NULL if
+** the program was run with elevated privilege (e.g., setuid or setgid
+** on Unix).  This can be used for cases like log file paths which
+** could otherwise be used for privilege escalation.  Note that some
+** platforms may have platform-specific privilege elevation mechanisms
+** not recognized by this function; see the implementation for details.
+*/
+NSPR_API(char*) PR_GetEnvSecure(const char *var);
+
+/*
 ** PR_SetEnv() -- set, unset or change an environment variable
 ** 
 ** Description: