TextView.h rearrage virtual methods for FBC

The order is updated so the virtual methods appear in the same order
that they did in BeOS R5 with methods new to Haiku added to the bottom.

Perform() moves up, all other methods move below GetDragParameters(),
the last virtual method in BeOS R5's TextView.h.
TextView: Fix FBC size breakage

In hrev46796 I added two new private methods: _PreviousLineStart(),
and _NextLineEnd() which increased the size of the class breaking
binary compatability because I forgot to decrement the reserved array.

This commit decrements the reserved array restoring the class size
to the original size fixing the binary compat issue.

Thanks Axel for noticing.
TextView: update comments

Private Method docs are/should be in doxygen format. Remove \brief as doxygen
doesn't need this if you document along side the method.

Remove brief description comments from public methods, you'll need to look in the
Haiku Book for this now.

style squash
TextView: include re-arrange style fix

* Put #include TextView.h first as our style guide suggests.
* Put #include <new> in it's own C++ includes section
* also remove an extra newline
TextView: Fix regression for Home and End

... while Shift is held down in a selection.

Before this commit, if you had some text selected and you pressed
Home or End with a Shift held down the selection would not change.
This was annoying and most likely unintentional. Thank you Axel for
informing me of this problem.

After this commit if you have some text selected and you press Home
with a Shift key held down it will move the end of the selection to the
first character of the same line that the end of selection is on and if you
press End with a Shift key held down it will move the end of the selection
to the last character of the same line that the end of the selection is on.

I looked at how a bunch of different OS's and applications handled this
and found that there are a bunch of different behaviors we could use here,
and there doesn't appear to be any consensus as to what the "right" or
"wrong" way to do this is so please forgive me if this doesn't work exactly
as you expect it to.

Note that the implementation used here is very different from how BeOS
R5 worked. In BeOS R5 pressing Home or End with Shift held down
always extended the selection, it never subtracted from it.

In BeOS pressing Home with Shift held down extended the selection from
the left-most part of the selection to the first charcter of the same line.
Pressing End with Shift held down extended the selection from the
right-most part of the selection to the end of the same line.