remove support for BSD/OS (closes bpo-31624) (#3812)

diff --git a/configure b/configure
index 819dc7a..cef9b6f 100755
--- a/configure
+++ b/configure
@@ -5703,13 +5703,6 @@
 fi
 rmdir CaseSensitiveTestDir
 
-case $MACHDEP in
-bsdos*)
-    case $CC in
-    gcc) CC="$CC -D_HAVE_BSDI";;
-    esac;;
-esac
-
 case $ac_sys_system in
 hp*|HP*)
     case $CC in
@@ -6263,8 +6256,8 @@
 
 
 case $MACHDEP in
-bsdos*|hp*|HP*)
-	# install -d does not work on BSDI or HP-UX
+hp*|HP*)
+	# install -d does not work on HP-UX
 	if test -z "$INSTALL"
 	then
 		INSTALL="${srcdir}/install-sh -c"
@@ -9228,9 +9221,6 @@
 	Linux*|GNU*|QNX*)
 		LDSHARED='$(CC) -shared'
 		LDCXXSHARED='$(CXX) -shared';;
-	BSD/OS*/4*)
-		LDSHARED="gcc -shared"
-		LDCXXSHARED="g++ -shared";;
 	FreeBSD*)
 		if [ "`$CC -dM -E - </dev/null | grep __ELF__`" != "" ]
 		then
@@ -9298,7 +9288,6 @@
 		 fi;;
 	Linux-android*) ;;
 	Linux*|GNU*) CCSHARED="-fPIC";;
-	BSD/OS*/4*) CCSHARED="-fpic";;
 	FreeBSD*|NetBSD*|OpenBSD*|DragonFly*) CCSHARED="-fPIC";;
 	OpenUNIX*|UnixWare*)
 		if test "$GCC" = "yes"
@@ -9325,7 +9314,6 @@
 	hp*|HP*)
 	    LINKFORSHARED="-Wl,-E -Wl,+s";;
 #	    LINKFORSHARED="-Wl,-E -Wl,+s -Wl,+b\$(BINLIBDEST)/lib-dynload";;
-	BSD/OS/4*) LINKFORSHARED="-Xlinker -export-dynamic";;
 	Linux-android*) LINKFORSHARED="-pie -Xlinker -export-dynamic";;
 	Linux*|GNU*) LINKFORSHARED="-Xlinker -export-dynamic";;
 	# -u libsys_s pulls in all symbols in libsys