Fix #> test fail on CCL-1.2 or later

The original test tried to skip reading the #> shorthand macro via:

    #-CCL-1.2 #>"blablabla..."

This did not work, as Clozure wouldn't then know how to skip the string
macro. To work around this, the M-string is now wrapped around a
with-input-from-string, eval'd at readtime.
Bump version number
Replace cl-syntax with named-readtables; bump version number

I haven't found a strong reason why cl-syntax is better than
its dependency named-readtables, so I moved over.
Add sourcehut mirror buildscript
Fix leading whitespace on folding M-string

If a folding block mode M-string starts with an initial line, it's
replaced with a Space (as how lines are joined together), like so:


    => " Foo"

This was a surprising result, and I called it a bug. The algorithm was
adjusted to find a natural fix, and four new assertions are added to the
test suite.
Reword the README a little bit better
Omit #> shorthand macro on Clozure CL 1.2 and later

The #> dispatch character is claimed on CCL since 1.2, as a macro to
read a keyword preserving case. I can't complain, since it's not
reserved to the user, but none of the reserved sharpsign macros really
speak to me as "This folds the following string" -- not even #" is safe.

The #> mstring macro is elided for all systems with the :CCL-1.2
feature, and its respective test is skipped.
Add mstring-reader shorthands

Instead of the function #'use-mstrings, the mstring reader itself is
exported from the package to allow lispers to attach it to whatever
dispatch character pair they want.

This allowed the reader to pick up on subchars and change the behavior
respectively; here, if the subchar is #\" or #\>, the block mode is
assumed and the reader immediately reads the following string.
Rename project to M-strings

The project was originally called Y-strings, because it was a crude
impersonation of YAML string-reading, and the letter Y catches the eye a
little bit.

A quick online search prompted me to change the name.
Add sourcehut test buildscript
Add test suite powered by Parachute
Incremental improvements