JDK-8176041 sped up parsing of comment lines, but was a bit too conservative and can be improved upon a bit:

- it breaks the fast path loop on backslashes, even though a backslash embedded in a comment line will never have any effect on subsequent logical lines
- it does two comparisons in the common case: testing c <= '\r' && c >= '\n' would mean only one comparison in the common case, since c is very likely to be > '\r' (also when reading from a byte stream)

While generally applicable, these optimizations speed up read of java.security by another ~10%, which has some relevance to bootstrap time on certain applications.