muscle: check the kind of api.prefix, api.location.type

muscle: check the kind of api.prefix, api.location.type

* data/bison.m4: Check api.prefix.
* data/c++.m4: Check api.location.type.
* doc/bison.texi: Fix uses of api.value.type, api.prefix, api.location.type.
Document {...} values for %define.
* src/parse-gram.y: Fix use of api.prefix.
* tests/calc.at: Fix uses of api.location.type.
* tests/input.at: Check api.prefix, and api.location.type.