Merge pull request #444 from TG9541/recover

#430 Forth Standard words CELLS CELL+ TRUE FALSE RSHIFT

lib/CELL+

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+\ https://forth-standard.org/standard/core/CELLPlus
+\ Add the size in address units of a cell to a-addr1, giving a-addr2
+#require ALIAS
+' 2+ ALIAS CELL+ ( a-addr1 -- a-addr2 )

lib/CELLS

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+\ https://forth-standard.org/standard/core/CELLS
+\ n2 is the size in address units of n1 cells.
+#require ALIAS
+' 2* ALIAS CELLS ( n1 -- n2 )

lib/FALSE

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+\ https://forth-standard.org/standard/core/FALSE
+\ Return a false flag.
+#require ALIAS
+' 0 ALIAS FALSE ( -- false )

lib/RSHIFT

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+\ STM8eForth : RSHIFT                                              TG9541-210417
+\ refer to github.com/TG9541/stm8ef/blob/master/LICENSE.md
+
+: RSHIFT ( n c - n )  \ shift n right c times
+  [ $5C  C,  \     INCW    X
+    $F6  C,  \     LD      A,(X)
+    $5C  C,  \     INCW    X
+    $4D  C,  \     TNZ     A
+    $2705 ,  \     JREQ    1$
+    $77  C,  \ 2$: SRA     (X)
+    $6601 ,  \     RRC     (1,X)
+    $4A  C,  \     DEC     A
+    $26F8 ,  \     JRNE    2$
+  ]          \ 1$:
+;

lib/TRUE

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+\ https://forth-standard.org/standard/core/TRUE
+\ Return a true flag, a single-cell value with all bits set.
+#require ALIAS
+' -1 ALIAS TRUE ( -- true )