picocom: bump to version 2.0

- Bump to version 2.0
- Switch the download site to GitHub
- Apply an upstream patch to fix a missing define
- Add a hash file
- Rewrap the help text to 72 characters length
- Change the official website

[Thomas: fix s/MAKE_ENV/TARGET_MAKE_ENV/.]

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>