2014-09-02: use (string->symbol str) instead of (call-with-input-string str

use (string->symbol str) instead of (call-with-input-string str read)

diff --git a/wisp-scheme.w b/wisp-scheme.w
--- a/wisp-scheme.w
+++ b/wisp-scheme.w
@@ -47,9 +47,9 @@ define : line-code line
 
 ; literal values I need
 define readcolon 
-       call-with-input-string ":" read
+       string->symbol ":"
 define readdot
-       call-with-input-string "." read
+       string->symbol "."
 
 define : line-continues? line
          equal? readdot : car : line-code line