Spell "boolean" as "Boolean". Reported by Akim Demaille.

Spell "boolean" as "Boolean".  Reported by Akim Demaille.
* data/bison.m4 (b4_percent_define_flag_if): Fix complaint.
* doc/bison.texinfo (Decl Summary): Fix.
* src/muscle_tab.c (muscle_percent_define_flag_if): Fix complaint.
* tests/input.at (Boolean %define variables): Update output.
* tests/skeletons.at (%define boolean variables: invalid skeleton
defaults): Rename to...
(%define Boolean variables: invalid skeleton defaults): ... this and
update output.