[lsp] enable backtraces in server
[lsp] enable backtraces in server

Whenever the server crashes, it should output the backtrace by default.

Signed-off-by: Rudi Grinberg <4c46c202a3b8207ad5740134b125aae40c6c67a8@gmail.com>

rgrinberg/merlin,the-lambda-church/merlin,ocaml/merlin,the-lambda-church/merlin,rgrinberg/merlin,ocaml/merlin,dra27/merlin,ocaml/merlin,rgrinberg/merlin,ocaml/merlin,rgrinberg/merlin,the-lambda-church/merlin,dra27/merlin,dra27/merlin,dra27/merlin