improve headers to better deal with removed-in-posix-2008 features

with this patch, setting _POSIX_SOURCE, or setting _POSIX_C_SOURCE or
_XOPEN_SOURCE to an old version, will bring back the interfaces that
were removed in POSIX 2008 - at least the ones i've covered so far,
which are gethostby*, usleep, and ualarm. if there are other functions
still in widespread use that were removed for which similar changes
would be beneficial, they can be added just like this.

include/netdb.h

@@ -118,21 +118,30 @@ struct protoent *getprotoent (void);
 struct protoent *getprotobyname (const char *);
 struct protoent *getprotobynumber (int);
 
+#if defined(_GNU_SOURCE) || defined(_BSD_SOURCE) || defined(_POSIX_SOURCE) \
+ || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE < 200809L) \
+ || (defined(_XOPEN_SOURCE) && _XOPEN_SOURCE < 700)
+struct hostent *gethostbyname (const char *);
+struct hostent *gethostbyaddr (const void *, socklen_t, int);
+#ifdef __GNUC__
+__attribute__((const))
+#endif
+int *__h_errno_location(void);
+#define h_errno (*__h_errno_location())
+#define HOST_NOT_FOUND 1
+#define TRY_AGAIN      2
+#define NO_RECOVERY    3
+#define NO_DATA        4
+#endif
+
 #if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
 const char *hstrerror(int);
-struct hostent *gethostbyname (const char *);
 int gethostbyname_r(const char *, struct hostent *, char *, size_t, struct hostent **, int *);
 int gethostbyname2_r(const char *, int, struct hostent *, char *, size_t, struct hostent **, int *);
 struct hostent *gethostbyname2(const char *, int);
-struct hostent *gethostbyaddr (const void *, socklen_t, int);
 int gethostbyaddr_r(const void *, socklen_t, int, struct hostent *, char *, size_t, struct hostent **, int *);
 int getservbyport_r(int, const char *, struct servent *, char *, size_t, struct servent **);
 int getservbyname_r(const char *, const char *, struct servent *, char *, size_t, struct servent **);
-#ifdef __GNUC__
-__attribute__((const))
-#endif
-int *__h_errno_location(void);
-#define h_errno (*__h_errno_location())
 #define EAI_NODATA     -5
 #define EAI_ADDRFAMILY -9
 #define EAI_INPROGRESS -100
@@ -143,10 +152,6 @@ int *__h_errno_location(void);
 #define EAI_IDN_ENCODE -105
 #define NI_MAXHOST 255
 #define NI_MAXSERV 32
-#define HOST_NOT_FOUND 1
-#define TRY_AGAIN      2
-#define NO_RECOVERY    3
-#define NO_DATA        4
 #endif
 
 

include/unistd.h

@@ -144,6 +144,12 @@ void encrypt(char *, int);
 void swab(const void *, void *, ssize_t);
 #endif
 
+#if defined(_GNU_SOURCE) || defined(_BSD_SOURCE) \
+ || (defined(_XOPEN_SOURCE) && _XOPEN_SOURCE < 700)
+int usleep(unsigned);
+unsigned ualarm(unsigned, unsigned);
+#endif
+
 #if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
 #define L_SET 0
 #define L_INCR 1
@@ -157,8 +163,6 @@ int getpagesize(void);
 int getdtablesize(void);
 int sethostname(const char *, size_t);
 int getdomainname(char *, size_t);
-int usleep(unsigned);
-unsigned ualarm(unsigned, unsigned);
 int setgroups(size_t, const gid_t []);
 char *getpass(const char *);
 int daemon(int, int);