Fix attempting to toggle visibility when tray disabled
Take two at fixing out of source builds
travis: Add clang & CPUs & fast_finish

HexChat seems to compile fine with clang so why to not test it too.
-j$(nproc) seems to work with HexChat and fast-finish marks build as
failed if one job fails.

Fast finish won't stop jobs that aren't finished at the time of failure.

Closes #1147
Fixed instances of hexchat_printf that unsafely used a string parameter as a format string.

Fixes #1153
Fix parsing of MONITOR responses

Fixes #1157
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