fix(util/thread): MULTI_THREAD=OFF mode
fix(util): compilation problems when using msys2

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(emacs/lean-type): change where to trigger eldoc

Previously, eldoc is triggered regardless of current position.
Now, it is triggered:

 - *NOT* looking-at whitespace or
 - looking-back end-parens such as ')', '}', ']', etc
chore(.travis.osx.yml): update homebrew lua package names

lua5.1: lua            => lua51
lua5.2: versions/lua52 => lua
fix(util/thread_script_state): make sure system does not crash during
finalization
fix(util/script_state_manager): crash when compiling with msys2 stack

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(util/thread_script_state): disable script_state recycling at finalization time

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>