Allow font change after GNU for matching the GFDL licence

gcc-4.7 man page include:
Permission is granted to copy, distribute and/or modify this document
under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with the
Invariant Sections being \*(L"\s-1GNU\s0 General Public License\*(R" and \*(L"Funding
Free Software\*(R", the Front-Cover texts being (a) (see below), and with
the Back-Cover Texts being (b) (see below).  A copy of the license is
included in the \fIgfdl\fR\|(7) man page.

Detect by allowing \s0 during matching of GNU Free Documentation License.

Signed-off-by: Niels Thykier <niels@thykier.net>
Move old false postive test case to their own subdirectory

Better for the human

Signed-off-by: Niels Thykier <niels@thykier.net>
Allow indenting text with pipe

Some package indent the license like this:
    | Permission is granted to copy, distribute and/or modify this
    | document under the terms of the GNU Free Documentation License,
    | version 1.3 or any later version published by the Free Software
    | Foundation; with no Invariant Sections, no Front-Cover Texts and
    | no Back-Cover Texts.  A copy of the license is included in the
    | section entitled "GNU Free Documentation License".

Allow it.

Signed-off-by: Niels Thykier <niels@thykier.net>
Allow verbatim \n in C strings

For gfdl detection allow verbatim \n in string, particularly in cstring

Signed-off-by: Niels Thykier <niels@thykier.net>
Allow (*note ) from info file

Some info file like gnash use note tag.

Allow it.

Signed-off-by: Niels Thykier <niels@thykier.net>
Fix false positive in xml file due to <link.*> </link>

Allow link tag

Signed-off-by: Niels Thykier <niels@thykier.net>
Allow <a> </a> tag for html

gnash use it. Allow it

Signed-off-by: Niels Thykier <niels@thykier.net>
c/standards-version: Bump ANCIENT_DATE

Signed-off-by: Niels Thykier <niels@thykier.net>
Fix #708957 when GFDL is used in template

Fix #708957 by allowing entities but only on well known files.
Indeed in other files, entities could be the phase of moon or even devil clauses.

Signed-off-by: Niels Thykier <niels@thykier.net>