Avoid CHA sequence for ANSI.SYS compatibility.

Github user @welash proposed a change in issue #73 in order to improve
the linenoise compatibility with older terminal emulators only able to
deal with a subset of ANSI sequences, notably ANSI.SYS and VT100
terminals strictly able to handle the original set of VT100 escape
sequences.

In order to improve the compatibility, the CHA sequence was removed and
translated to move 999 positions to the left, then move on the right
for the desired number of positions. The CHA sequence was apparently
added only with VT220, that's why it is not available everywhere.

This commit features almost exactly the change proposed in issue #73
with a small fix for a bug in multi-line editing mode introduced by the
patch.
Better specify the set of escapes used.
Don't emit ESC [ n C with n=0.

This fixes a bug introduced with ANSI.SYS compatibility.
When we want to move at a specific column, we need to emit the sequence
to move the cursor to the right (after we moved 999 positions to the left)
only if we want to actually move right at least 1 position, since a
count of zero will still move the cursor one position to the right.
Replace ESC 999D with CR.

OSX default Terminal app does not handle 999D well, the cursor will wrap
back to the previous row in the last colum, instead of ignoring the
sequence if the cursor is already at the left edge.

In order to avoid reintroducing the nG sequence that is not compatible
with base VT100 emulation and ANSI.SYS, we use CR that should be
hopefully widely supported.
Move to end before return when in multi-line mode.

This makes sure that if we are editing in multi-line mode a line that
actually spawns across multiple lines, the next output performed by the
application using linenoise will not overwrite the edited line.
License file added.

However the files linenose.c and linenose.h already had inline licenses.