eqn macros mistreat string arguments

[Doug McIlroy]

Gnu eqn incorrectly deems quoted commas in macro calls to be argument
separators. This example evokes the diagnostic, `newline before end of
quoted text':
        .EQ
        define f % $1 %
        f("a,b")
        .EN
This violates a cardinal rule that dates from the original eqn man page:
`Strings enclosed in double quotes " " are passed through untouched.'

Norman Wilson confirms that the Research implementation of eqn circa
v10 handles the example correctly. (V10 was the earliest printed manual
to describe macros with arguments. Though it does not overtly explain
comma-hiding, it does assert the cardinal rule.)

Doug McIlroy