rename "WORD" lexical token to "BAREWORD"

rename "WORD" lexical token to "BAREWORD"

The enum value "WORD" can apparently clash with a enum value in windows
headers.  It used to be worked around in windows by #defining YYTOKENTYPE,
which caused the

    enum yytokentype {
        ...
        WORD = ...;
    }

in perly.h to be skipped, while still using the

    #define WORD ...

which appears later in the same file.

In bison 3.x, the auto-generated perl.h no longer includes the #defines,
so this workaround no longer works.

Instead, change the name of the token from "WORD" to "BAREWORD".