Please check :FUZE option in USE-SYNTAX

The named-readtables can ignore conflicts of macro characters by `:FUZE` option.
`NAME-READTABLES:IN-READTABLE` does not ignore `:FUZE` options.

But, `CL-SYNTAX:USE-SYNTAX` just ignores `:FUZE` options; signaling `NAMED-READTABLES:READER-MACRO-CONFLICT` condition causes always invoking the debugger while a `:FUZE` option has been specified for the conflicted syntax.

This patch might fix this problem.

Testing example: https://github.com/ichimal/windows-path-reader.
The `windows-path-reader` assigns original reader to `#"` with `:FUZE` option.

The CLHS defines a macro-dispatch-character `#"` as *undefined* (not *undefined**).
On GNU CLISP, `#"` is assigned the `SYSTEM::CLISP-PATHNAME-READER` (this is system default).
So, using `USE-SYNTAX` for `windows-path-header` on CLISP always invokes a debugger with continuable error.