Fix spurious conform test failures

[Zack Weinberg]

Since it's not particularly difficult to write a Perl regex that
matches C string constants *with* \-escapes taken into account, can I
suggest we do that now instead of when we trip over it?  Also, should
do the same thing for character
constants.

    # Discard string and character constants.  Since this is preprocessor
    # output we need not worry about \-newline or un-terminated strings,
    # and since we just need to find the end, we don't need to distinguish
    # the various types of \-escapes.
    $str =~ s/" (?: [^"\\] | \\. )* "//xg;
    $str =~ s/' (?: [^'\\] | \\. )* '//xg;

zw