[vala/staging] posix: Fix crypt(3), now that we have feature test macros.

[Dr. Michael Lauer <mlauer src gnome org>]

commit d3b8aa3734656c589fb6f6555ce21fbc77bbfc88
Author: Dr. Michael Lauer <mickey vanille-media de>
Date:   Tue Mar 6 16:29:25 2018 +0100

    posix: Fix crypt(3), now that we have feature test macros.
    
    Note that crypt(3) returns 'null' on error.

 vapi/posix.vapi |   12 ++----------
 1 files changed, 2 insertions(+), 10 deletions(-)
---
diff --git a/vapi/posix.vapi b/vapi/posix.vapi
index 155e704..5265ab5 100644
--- a/vapi/posix.vapi
+++ b/vapi/posix.vapi
@@ -2126,16 +2126,8 @@ namespace Posix {
        [Version (deprecated_since = "POSIX.2", replacement = "termios ECHO flag")]
        [CCode (cheader_filename = "unistd.h")]
        public unowned string getpass (string promt);
-       /**
-        * Encodes a string
-        *
-        * To expose Posix crypt() GNU's libc and others require the feature test
-        * macro _XOPEN_SOURCE to be defined. See man 3 crypt.
-        * A VAPI is unable to define and emit this macro before all include files
-        * Instead use valac -X -D_XOPEN_SOURCE
-        */
-       [CCode (cheader_filename = "unistd.h")]
-       public unowned string crypt (string key, string salt);
+       [CCode (cheader_filename = "unistd.h", feature_test_macro = "_XOPEN_SOURCE")]
+       public unowned string? crypt (string key, string salt);
        [CCode (cheader_filename = "unistd.h")]
        public int getpagesize ();
        [CCode (cheader_filename = "unistd.h")]