remove IRIX support (closes bpo-31341) (#3310)

See PEP 11.
diff --git a/configure b/configure
index 5b742b8..d2766bc 100755
--- a/configure
+++ b/configure
@@ -2994,12 +2994,6 @@
 
 
 # The later defininition of _XOPEN_SOURCE and _POSIX_C_SOURCE disables
-# u_int on Irix 5.3. Defining _BSD_TYPES brings it back.
-
-$as_echo "#define _BSD_TYPES 1" >>confdefs.h
-
-
-# The later defininition of _XOPEN_SOURCE and _POSIX_C_SOURCE disables
 # certain features on Mac OS X, so we need _DARWIN_C_SOURCE to re-enable
 # them.
 
@@ -3298,7 +3292,6 @@
 	linux*) MACHDEP="linux";;
 	cygwin*) MACHDEP="cygwin";;
 	darwin*) MACHDEP="darwin";;
-	irix646) MACHDEP="irix6";;
 	'')	MACHDEP="unknown";;
     esac
 fi
@@ -9136,7 +9129,7 @@
 $as_echo "$SHLIB_SUFFIX" >&6; }
 
 # LDSHARED is the ld *command* used to create shared library
-# -- "cc -G" on SunOS 5.x, "ld -shared" on IRIX 5
+# -- "cc -G" on SunOS 5.x.
 # (Shared libraries in this instance are shared modules to be loaded into
 # Python, as opposed to building Python itself as a shared library.)
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking LDSHARED" >&5
@@ -9148,8 +9141,6 @@
 		BLDSHARED="Modules/ld_so_aix \$(CC) -bI:Modules/python.exp"
 		LDSHARED="\$(LIBPL)/ld_so_aix \$(CC) -bI:\$(LIBPL)/python.exp"
 		;;
-	IRIX/5*) LDSHARED="ld -shared";;
-	IRIX*/6*) LDSHARED="ld ${SGI_ABI} -shared -all";;
 	SunOS/5*)
 		if test "$GCC" = "yes" ; then
 			LDSHARED='$(CC) -shared'
@@ -9309,10 +9300,6 @@
 		then CCSHARED="-fPIC"
 		else CCSHARED="-Kpic -belf"
 		fi;;
-	IRIX*/6*)  case $CC in
-		   *gcc*) CCSHARED="-shared";;
-		   *) CCSHARED="";;
-		   esac;;
 	esac
 fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $CCSHARED" >&5