Follow cl-xkbcommon 767be00: modifier keywords as a type
A keyword that names no modifier is now a type-error, since the
functions that take a modifier declare the new type modifier-keyword.
The reference describes the type, Concepts names it beside the
keywords, and Errors and Logging and Keyboard States and Modifiers say
which error a wrong keyword and a wrong name signal, quoting SBCL's
message for the keyword.
make-context takes :log-limit, the most log messages a context keeps,
which was a fixed 100. The reference, Contexts and Keymaps, and Errors
and Logging say so, and Errors and Logging says that an error reports
only the messages of the compile that failed. modifier-active-p lists
the modifier keywords in the order active-modifiers returns them, and
Platforms and Testing names the environment among what cl-xkbcommon
takes from SBCL.
