Fix some typos.

Fix some typos.

Get rid of the paragraph about C++-style comments at the beginning of
the document, as it also appears in section 1.1.1 "Comments".

Add a section on how to extract data from packets, which explains the
"pd" and "offset" arguments to a dissector, and notes that you should
not just blithely cast pointers into the packet data to 2-byte or 4-byte
integral types and dereference them, as the pointer may not be aligned,
and the field may not have the same byte order as the processor on which
Ethereal is running (in fact, it's probably *guaranteed* not to on at
least one machine, as Ethereal runs on both big-endian and little-endian
platforms...).

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@1710 f5534014-38df-0310-8fa8-9805f1628bb7