missing from cython's libc pxd tree

pyrex/xlibc/stdarg.pxd

+cdef extern from "stdarg.h":
+
+    # The type of va_list is not a standard definition.
+    # This should be a rather opaque type.
+    ctypedef void * va_list
+
+    # va_arg support is not possible in Pyrex.  Some hard-coded types
+    # are available in pyrex_helpers.pyx.
+    void va_start(va_list ap, last)
+    void va_copy(va_list dest, va_list src)
+    void va_end(va_list ap)