use config.def.h mechanism
add SHELL in config.h

along with duration in config.h, factored some code in tnew()/treset()
and cleaned some code.

results in a lot of simplification :
	- no more dirty flags (perf are good enough).
	- no more ugly gfx call in emulation functions.
LINESPACE removed from config.h.
BORDER is now handled correctly.

visibility of the cursor is not saved/loaded anymore.
scrolling up/down is fixed.
added RI and RIS sequences.
fixed cursor drawing bug.

cursor keys are handled in kpress according to the Application Mode (DECPAM).
define & enum were renamed.
tcursor() is now tmovecursor() which is more correct.
tcpos() is now tcursor(), as DECSC is also supposed to save attributes.
capnames are indicated whenever possible.

Currently:
alsamixer looks fine, totally usable.
ncmpc is almost ok.
emacs looks like shit.