configure: remove support for obsolete platforms

- #error hack for MIPSpro compiler from unix/clock-*
- irix exclusions from unix/*iconv
- hpux defines from unix/{getifaddrs,ipv6ifname} (the obsolete
  hpuxi-g++-64 spec would add them automatically anyway)

Change-Id: Ib227e5626c0e8c8f6faebf76c312d77955f80b92
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

config.tests/unix/clock-gettime/clock-gettime.cpp

@@ -47,8 +47,6 @@ int main(int, char **)
     clock_gettime(CLOCK_REALTIME, &ts);
 #else
 #  error "Feature _POSIX_TIMERS not available"
-    // MIPSpro doesn't understand #error, so force a compiler error
-    force_compiler_error = true;
 #endif
     return 0;
 }

config.tests/unix/clock-monotonic/clock-monotonic.cpp

@@ -47,8 +47,6 @@ int main(int, char **)
     clock_gettime(CLOCK_MONOTONIC, &ts);
 #else
 #  error "Feature _POSIX_MONOTONIC_CLOCK not available"
-    // MIPSpro doesn't understand #error, so force a compiler error
-    force_compiler_error = true;
 #endif
     return 0;
 }

config.tests/unix/getifaddrs/getifaddrs.cpp

@@ -40,10 +40,6 @@
 /* Sample program for configure to test for if_nametoindex support
 on target platforms. */
 
-#if defined(__hpux)
-#define _HPUX_SOURCE
-#endif
-
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <net/if.h>

config.tests/unix/gnu-libiconv/gnu-libiconv.cpp

@@ -37,9 +37,6 @@
 **
 ****************************************************************************/
 
-#if defined(__sgi)
-#error "iconv not supported on IRIX"
-#else
 #include <iconv.h>
 
 int main(int, char **)
@@ -55,4 +52,3 @@ int main(int, char **)
 
     return 0;
 }
-#endif

config.tests/unix/iconv/iconv.cpp

@@ -37,9 +37,6 @@
 **
 ****************************************************************************/
 
-#if defined(__sgi)
-#error "iconv not supported on IRIX"
-#else
 #include <iconv.h>
 
 int main(int, char **)
@@ -55,4 +52,3 @@ int main(int, char **)
 
     return 0;
 }
-#endif

config.tests/unix/ipv6ifname/ipv6ifname.cpp

@@ -40,10 +40,6 @@
 /* Sample program for configure to test for if_nametoindex support
 on target platforms. */
 
-#if defined(__hpux)
-#define _HPUX_SOURCE
-#endif
-
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <net/if.h>