Add terminfo definitions for terminals with meta key

Some programs don't check the value of km and use smm and rmm
capabilites, and they cause the terminal change to meta enabled
mode even in cases where is not desirable.

Allmost all people is using the terminal waiting that meta sends
escape, so rmm and smm are not needed. If someone needs meta
sets 8 bit he can use the correct terminfo definition in TERM.
Correcting the bitmask value check.
Tmux is using C-b by default.

Thanks for noticing Fidel Barrera Cruz!
Regarding commit 7e3cff3

Hello.

I reviewed and tested commit 7e3cff3, and made a patch that fixes some
problems in it.

1. There's a semicolon after an if statement, which is obviously a
typo.

2. The current way of calculating text position in "xdraws" yields
inconsistent results in some cases. This is due to the use of
"font->width", which varies. Instead, "xw.cw" has to be used as the
character width.

Sincerely,
Eon
Correctly initialize altscreen when defaultbg is not 0.

The alternate screen is not properly initialized when st starts. To see
this, set defaultbg in config.h to anything other than 0 (for example, swap
defaultfg and defaultbg), and run:

./st -e sh -c 'tput smcup; read'

You should see that the top-left 80x24 rectangle is black (or whatever
colorname[0] is), while the rest of the screen (if any) has the desired
colorname[defaultbg] color.

The attached patch fixes this by initializing term.c.attr in tnew() before
calling tresize(). It also removes the unnecessary xcalloc() calls, which
misled me on this bug hunt since it is really tclearregion() which
initializes term.lines and term.alt in tresize().
Adding some contributors. Thanks to you all!
Wide character support.

Thanks "Eon S. Jeon" <esjeon@hyunmu.am>!