add posix.stdlib library

Cython/Includes/posix/stdlib.pxd

+# POSIX additions to <stdlib.h>
+# http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stdlib.h.html
+
+cdef extern from "stdlib.h" nogil:
+    void   _Exit(int)
+    double drand48()
+    double erand48(unsigned short *)
+    int    getsubopt(char **, char *const *, char **)
+    void   lcong48(unsigned short *)
+    long   lrand()
+    char  *mkdtemp(char *)
+    int    mkstemp(char *)
+    long   mrand()
+    long   nrand48(unsigned short *)
+    int    posix_memalign(void **, size_t, size_t)
+    int    posix_openpt(int)
+    char  *ptsname(int)
+    int    putenv(char *)
+    int    rand_r(unsigned *)
+    long   random()
+    char  *realpath(const char *, char *)
+    unsigned short *seed48(unsigned short *)
+    int    setenv(const char *, const char *, int)
+    void   setkey(const char *)
+    char  *setstate(char *)
+    void   srand48(long)
+    void   srandom(unsigned)
+    int    unlockpt(int)
+    int    unsetenv(const char *)

tests/compile/posix_pxds.pyx

@@ -18,3 +18,7 @@ from posix.types cimport *
 cimport posix.stat
 from posix cimport stat
 from posix.stat cimport *
+
+cimport posix.stdlib
+from posix cimport stdlib
+from posix.stdlib cimport *