how to specify the readtable to be used when swank is handling request from slime

[Attila Lendvai]

FYI, i have a long forgotten related fix in my branch:

https://github.com/attila-lendvai/slime/commit/ae2addfa29a061d42d0fc69fb2206175a1709f6b

-- 
• attila lendvai
• PGP: 963F 5D5F 45C7 DFCD 0A39
--
“[...] so long as the people do not care to exercise their freedom,
those who wish to tyrannize will do so; for tyrants are active and
ardent, and will devote themselves in the name of any number of gods,
religious and otherwise, to put shackles upon sleeping men.”
	— Voltaire (1694–1778), 'Anarchism & American Traditions' (1908)