Create a new section of pyport.h to hold all external function declarations

for systems that are missing those declarations from system include files.
Start by moving a pointy-haired ones from their previous locations to the
new section.

(The gethostname() one, for instance, breaks on several systems, because
some define it as (char *, size_t) and some as (char *, int).)

I purposely decided not to include the summary of used #defines like Tim did
in the first section of pyport.h. In my opinion, the number of #defines
likedly to be used by this section would make such an overview unwieldy. I
would suggest documenting the non-obvious ones, though.

Modules/socketmodule.c

@@ -110,10 +110,6 @@ Socket methods:
 #include <unistd.h>
 #endif
 
-#if !defined(MS_WINDOWS) && !defined(PYOS_OS2) && !defined(__BEOS__)
-extern int gethostname(char *, size_t); /* For Solaris, at least */
-#endif
-
 #if defined(PYCC_VACPP)
 #include <types.h>
 #include <io.h>
@@ -129,11 +125,6 @@ extern int gethostname(char *, size_t); /* For Solaris, at least */
 #include <os2.h>
 #endif
 
-#if defined(__BEOS__)
-/* It's in the libs, but not the headers... - [cjh] */
-int shutdown( int, int );
-#endif
-
 #include <sys/types.h>
 #include "mytime.h"
 
@@ -2407,9 +2398,9 @@ shutdown() -- shut down traffic in one or both directions\n\
 
 DL_EXPORT(void)
 #if defined(MS_WINDOWS) || defined(PYOS_OS2) || defined(__BEOS__)
-init_socket()
+init_socket(void)
 #else
-initsocket()
+initsocket(void)
 #endif
 {
 	PyObject *m, *d;