Fix textbox not scrolling to to bottom on resize

Set buf->scrollbar_down conditionally when vertically resizing text window
If resize to enlarge appears to go to last line, set buf->scrollbar_down to be sure.

Fixes #1151
Closes #1171
Remove old config migration

Fixes #1194
configure: Fix checking for perl

Closes #1196
Fixes #1197
Warning cleanup

- ignoring const
- declarations after statements
- some C files didnt include own headers (risking them getting out of sync)

Closes #1064
ssl: Don't use global openssl context

Fixes #789
ssl: Use more secure options

This disables ssl 2/3
ssl: Validate hostnames

Closes #524
Fix possible crash in SASL Blowfish mech