R7RS: Add #\null -> #\nul and #\escape -> #\esc.

LOG

@@ -1137,3 +1137,4 @@
   generated config.h.  Instead removed InstallPrefix entirely so
   it isn't an attractive hazzard.
     configure, makefiles/Mf-install.in
+- add #\null and #\escape as aliases for #\nul and #\esc (R7RS compatibility)

mats/6.ms

@@ -1531,6 +1531,9 @@
   (eqv? (char-name 'rubout) #\rubout)
   (eqv? (char-name #\nul) 'nul)
   (eqv? (char-name 'nul) #\nul)
+  (eqv? (char-name #\null) 'nul)
+  (eqv? (char-name 'null) #\nul)
+  (eqv? #\nul #\null)
   (eqv? (char-name 'foo) #f)
   (eqv? (char-name 'delete) #\delete)
   (eqv? (char-name #\delete) 'delete)
@@ -1540,6 +1543,9 @@
   (eqv? (char-name #\alarm) 'alarm)
   (eqv? (char-name 'esc) #\esc)
   (eqv? (char-name #\esc) 'esc)
+  (eqv? (char-name 'escape) #\esc)
+  (eqv? (char-name #\escape) 'esc)
+  (eqv? #\esc #\escape)
   (error? (read (open-input-string "#\\foo")))
   (and (eqv? (char-name 'foo #\003) (void))
        (eqv? (char-name 'foo) #\003)

s/read.ss

@@ -1856,9 +1856,11 @@
   (char-name 'newline #\newline) ; must come after linefeed entry
   (char-name 'backspace #\backspace)
   (char-name 'rubout #\rubout)
+  (char-name 'null #\nul)
   (char-name 'nul #\nul)
   (char-name 'bel #\bel)
   (char-name 'vt #\vt)
+  (char-name 'escape #\esc)
   (char-name 'esc #\esc)
   (char-name 'vtab #\vtab)
   (char-name 'delete #\rubout)