Mention special handling of some extra fields, like in _set

man/zip_file_extra_field_get.mdoc

diff --git a/man/zip_file_extra_field_get.mdoc b/man/zip_file_extra_field_get.mdoc
index 64f50c3..c2cfdc9 100644
--- a/man/zip_file_extra_field_get.mdoc
+++ b/man/zip_file_extra_field_get.mdoc
@@ -1,5 +1,5 @@
 .\" zip_file_extra_field_get.mdoc -- get extra field for file in zip
-.\" Copyright (C) 2012-2013 Dieter Baron and Thomas Klausner
+.\" Copyright (C) 2012-2014 Dieter Baron and Thomas Klausner
 .\"
 .\" This file is part of libzip, a library to manipulate ZIP files.
 .\" The authors can be contacted at <libzip@nih.at>
@@ -29,7 +29,7 @@
 .\" OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
 .\" IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd February 20, 2013
+.Dd October 8, 2014
 .Dt ZIP_FILE_EXTRA_FIELD_GET 3
 .Os
 .Sh NAME
@@ -146,3 +146,11 @@
 .An Dieter Baron Aq Mt dillo@nih.at
 and
 .An Thomas Klausner Aq Mt tk@giga.or.at
+.Sh CAVEATS
+Please note that the extra field IDs 0x0001 (ZIP64 extension),
+0x6375 (Infozip UTF-8 comment), and
+0x7075 (Infozip UTF-8 file name) can not be read using
+.Fn zip_file_extra_field_get
+since they are used by
+.Xr libzip 3
+internally.