extra words: allow finer-grained loading

blk/102

@@ -1,6 +1,6 @@
-50 LOAD+ ( B152, extras )
+'? CASE NOT [IF] 51 52 LOADR+ [THEN] DROP ( B152-153 )
+'? FILL NOT [IF] 53 LOAD+ [THEN] DROP ( B154 )
 1 7 LOADR+
-
 : BROWSE
     0 ACC ! L
     BEGIN

blk/150

@@ -1,6 +1,6 @@
 Extra words
 
-The Core words (B420) section contains the absolute minimum
+The Core words (B350) section contains the absolute minimum
 needed to get a usable Forth interpreter with input buffer and
 disk blocks access running. The goal here is to minimize the
 binary size of a minimum Collapse OS install.
@@ -10,5 +10,6 @@ are generally useful. They are so useful that they are part
 of the Dictionary (B30).
 
 Some programs need them, so they will automatically LOAD them.
-To that end, the loader is conditional: it aborts if extra
-words are already present. Load with "152 LOAD".
+Because more than one program can use the same extra words,
+conditional loaders are recommended. If you want to load all
+words do "152 LOAD" which conditionally loads all extra words.

blk/152

@@ -1,3 +1,4 @@
-'? CASE NOT [IF]
-    1 5 LOADR+
-[THEN] DROP ( from '? )
+'? CASE NOT [IF] 1 2 LOADR+ [THEN] DROP ( from '? )
+'? FILL NOT [IF] 3 LOAD+ [THEN] DROP
+'? EMPTY NOT [IF] 4 LOAD+ [THEN] DROP
+'? WIPE NOT [IF] 5 LOAD+ [THEN] DROP