Fix bug with signal handling in catch.c

Fix a bug where double-tap of a modifier didn't work unless a hotkey keypress was also defined. This revealed a bug in how weak references were used. isEqual: uses pointer equality by default, so it doesn't work on arrays of weak refs. I hacked around it by implementing isEqual: for the one class I care about.

Signal handlers might be called repeatedly. As such they can't call
non-async-safe functions such as printf. Instead set a sentinel and
check for it.

Release URL codes when they're no longer needed. A mark is placed at the beginning and end of the URL. The one at the beginning is needed to keep the reference count to the code around until the one at the end is added. These marks are saved and restored.

More OSC 8 changes: use colons to delimit params and hover adjacent links together if their URLs and IDs are equal, or if the URLs are equal and the IDs are both unspecified.

profiles are sensible.

Add more logging to track down the source of mysterious drags. Seems they're not being started through the expected code path that takes minimum distance into account.

Update OSC 8 to require parameters prior to the URL. A difference in parameters prevents hover-underlining together.

The new syntax is:

OSC 8 ; params ; url ST

params are (for now) space delimited ASCII and may not contain a ;.
url is a URL. I'm more accepting that I have to be and will take UTF-8 encoded URLs that aren't properly percent-escaped.

Auto hide find cursor window when the session that created it ceases to be first responder. Issue 5637

Add crashlog messages to pinned messages so that you can create a debug log to report issues like the tab bar going bonkers.

Get rid of a gross hack when dragging the only tab in a window. We used to move the window to a hopefully offscreen coordinate of -10000,-10000. That's not guaranteed to work and is silly. Instead, order it out. This tickled another design issue where a placeholder cell was removed while it still had a tracking rect. This commit prevents that crash by first removing the tracking rect.

Add support for cmd-click file:line:col and VSCode.

Change "Open in current space" for hotkey windows to move the hotkey window to the current space if it's already open on another space when the hotkey is pressed. Issue 5622.

Add an experimental feature to draw an outline around underline and vertical bar cursors to improve distinction from text. Suggested in issue 4614.

Spit out the diffs as a base64 encoded tarball because file.io is dead and using AWS to get these files through Travis's supported artifacts API is way too much work

There's a hack to make the app active when the space changes to a lion fullscreen window and the app isn't active. This is needed only for LSUIElement apps, where the OS gets confused. Limit the hack to LSUIElement mode since you could use spaces and have two monitors. Issue 5489.