Configure: I remove adding of -D_XPG4_2 -D__EXTENSIONS__ in sctp builds for

following reasons:

- it's not the way to engage XPG4v2 mode, defining _XOPEN_SOURCE to
  value less than 500 is (see standards(5));
- we need to work out strategy to handle _XOPEN_SOURCE, current state
  when we define e.g. _XOPEN_SOURCE to 500 in some files is inappropriate;
- sctp implementation on Solaris is incomplete, in sense that bss_dgram.c
  doesn't compile, because not all structures are defined, so that
  enabling sctp doesn't work anyway;

Configure

@@ -1449,14 +1449,6 @@ if (!$IsMK1MF)
 		}
 	}
 
-if (!defined($disabled{"sctp"}))
-	{
-	if ($target =~ /^solaris/)
-		{
-		$cflags = "$cflags -D_XPG4_2 -D__EXTENSIONS__";
-		}
-	}
-
 $cpuid_obj.=" uplink.o uplink-x86.o" if ($cflags =~ /\-DOPENSSL_USE_APPLINK/);
 
 #