Do not pass the -fms-extensions flag, it is unsupported on OpenBSD and
breaks the build.

Index: configure
--- configure.orig
+++ configure
@@ -12764,35 +12764,6 @@ fi
 # Checks for programs.
 
 
-# Copied from http://stackoverflow.com/a/10682813/9832 and tweaked for C (as
-# opposed to C++)
-#
-# AX_CHECK_CFLAGS(ADDITIONAL-CFLAGS, ACTION-IF-FOUND, ACTION-IF-NOT-FOUND)
-#
-# checks whether the $(CC) compiler accepts the ADDITIONAL-CFLAGS
-# if so, they are added to the CXXFLAGS
-
-
-  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether compiler accepts \"-fms-extensions\"" >&5
-printf %s "checking whether compiler accepts \"-fms-extensions\"... " >&6; }
-  cat > conftest.c << EOF
-  int main(){
-    return 0;
-  }
-EOF
-  if $CC $CFLAGS -o conftest.o conftest.c -fms-extensions > /dev/null 2>&1
-  then
-    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: yes" >&5
-printf "%s\n" "yes" >&6; }
-    CFLAGS="${CFLAGS} -fms-extensions"
-
-  else
-    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
-printf "%s\n" "no" >&6; }
-
-  fi
-
-
 # We will add this back for non-debug builds in the common.mk file
 CFLAGS=`echo ${CFLAGS} | sed 's/-O2//'`
 CXXFLAGS=`echo ${CXXFLAGS} | sed 's/-O2//'`