Fix test colorization
improved symbol printing
Merge branch 'print' of https://github.com/6502/jscl

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Add clarifing comment
Add ALPHA-CHAR-P. FIND and FIND-If work also on sequences
The reader will ignore expressiones prefixed with #+nil
Rewrite and simplify potential-number-p according to the spec rules.

The previous implementation failed with '+' and '-' as input.
Escape token also for the package prefix
Update AUTHORS file
Fix read-float. Define CHAR-UPCASE and CHAR-DOWNCASE
Update name in CREDITS
Create JSCL package to keep the symbols in the host implementation

We can manage what symbols are accesible from JSCL and avoid
collisions. In particular, this fixes the compilation in GNU/clisp,
which failed because it exports a with-collect macro in the EXT
package, visible from CL-USER.
Update build instructions