Closer still on asm.js

Split apart boot.fs some more.

common/extra3.fs

@@ -0,0 +1,17 @@
+\ Copyright 2022 Bradley D. Nelson
+\
+\ Licensed under the Apache License, Version 2.0 (the "License");
+\ you may not use this file except in compliance with the License.
+\ You may obtain a copy of the License at
+\
+\     http://www.apache.org/licenses/LICENSE-2.0
+\
+\ Unless required by applicable law or agreed to in writing, software
+\ distributed under the License is distributed on an "AS IS" BASIS,
+\ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+\ See the License for the specific language governing permissions and
+\ limitations under the License.
+
+: fsqrt ( r -- r ) 1e 20 0 do fover fover f/ f+ 0.5e f* loop fnip ;
+
+3.14159265359e fconstant pi