Honor directive parameters after a quoted filename reference (#2457)

Honor directive parameters after a quoted filename reference (#2457)

For example, the following ACL did not match `example.com`:

    acl foo dstdomain "file-of-domains.txt" example.com

strtokFile() implements the "read directive parameters from a quoted
file" syntax used when configuration_includes_quoted_values is off (the
documented default). Once the named file's lines were exhausted,
strtokFile() returned nullptr, signalling end-of-directive to callers
such as ACLDomainData::parse(). Any tokens following the quoted filename
on the same configuration line (e.g., "example.com" above) were silently
discarded. A parameter file reference and trailing literal parameters
are valid syntax individually; combining them on one line has always
been allowed by the grammar, so the omission was "invisible" to admins.

This bug dates back to 2008 commit f32cd13e ("Replace cnfig parser gotos
with do-while loop."), which replaced a goto that resumed parsing after
the file's last line with an unconditional "return nullptr". Every Squid
release starting with v3.1.0.1 is affected.