Improve execsh() and don't allow anonymous shells

This patch improves the shell selection on execsh and forbid
shell with users don't registered in the passwd file.
Add eschandle()

We already have a csihandle() function, where is located code about
CSI sequences, so it is logical do the same with ESC sequences.
This change helps to simplify tcontrol(), which has a complex flow
and should be rewritten.
Improve readability of enum members

The 'left shift from one' notation of power of two integers is more
expressive than the result.

Signed-off-by: Alexander Huemer <alexander.huemer@xx.vu>
Signed-off-by: Roberto E. Vargas Caballero <k0ga@shike2.com>
Move calls to selsnap into selnormalize

This simplifies getbuttoninfo() and bpress(), and fixes a bug which made word
snapping behave incorrectly when a delimiter was at the beginning or end of
line.

Signed-off-by: Roberto E. Vargas Caballero <k0ga@shike2.com>
Change the behavior of word snapping on delimiters

This makes any sequence of identical delimiters be considered a single
word in word-snapping mode. This seems more coherent for this mode and
is similar to what xterm does.

Signed-off-by: Roberto E. Vargas Caballero <k0ga@shike2.com>
Removing wrapping newlines from selection

When getting selected text, lines that were wrapped because of length
ought not include the wrapping newline in the selection.

This comes up, for example, when copying a bash command that is long
enough to wrap from the console and pasting it back into the console.
The extra newline breaks it.

Similiarly, changes behavior when trimming whitespace from the end of a
physical line to only do so if the line does not wrap. Otherwise we are
trimming whitespace from the middle of a logical line, which may change
its meaning.

Signed-off-by: Roberto E. Vargas Caballero <k0ga@shike2.com>
Remove indentation level in xdrawcursor