lib/ur: Implement crash (panic) reporting (fixes #959) (#5702)

* lib/ur: Implement crash (panic) reporting (fixes #959)

This implements a simple crash reporting method. It piggybacks on the
panic log files created by the monitor process, picking these up and
uploading them from the usage reporting routine.

A new config value points to the crash receiver base URL, which defaults
to "https://crash.syncthing.net/newcrash" (following the pattern of
"https://data.syncthing.net/newdata" for usage reports, but allowing us
to separate the service as required).

go.sum

@@ -19,6 +19,8 @@ github.com/calmh/xdr v1.1.0 h1:U/Dd4CXNLoo8EiQ4ulJUXkgO1/EyQLgDKLgpY1SOoJE=
 github.com/calmh/xdr v1.1.0/go.mod h1:E8sz2ByAdXC8MbANf1LCRYzedSnnc+/sXXJs/PVqoeg=
 github.com/ccding/go-stun v0.0.0-20180726100737-be486d185f3d h1:As4937T5NVbJ/DmZT9z33pyLEprMd6CUSfhbmMY57Io=
 github.com/ccding/go-stun v0.0.0-20180726100737-be486d185f3d/go.mod h1:3FK1bMar37f7jqVY7q/63k3OMX1c47pGCufzt3X0sYE=
+github.com/certifi/gocertifi v0.0.0-20190506164543-d2eda7129713 h1:UNOqI3EKhvbqV8f1Vm3NIwkrhq388sGCeAH2Op7w0rc=
+github.com/certifi/gocertifi v0.0.0-20190506164543-d2eda7129713/go.mod h1:GJKEexRPVJrBSOjoqN5VNOIKJ5Q3RViH6eu3puDRwx4=
 github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=
 github.com/cheekybits/genny v1.0.0 h1:uGGa4nei+j20rOSeDeP5Of12XVm7TGUd4dJA9RDitfE=
 github.com/cheekybits/genny v1.0.0/go.mod h1:+tQajlRqAUrPI7DOSpB0XAqZYtQakVtB7wXkRAgjxjQ=
@@ -34,6 +36,8 @@ github.com/flynn-archive/go-shlex v0.0.0-20150515145356-3f9db97f8568 h1:BMXYYRWT
 github.com/flynn-archive/go-shlex v0.0.0-20150515145356-3f9db97f8568/go.mod h1:rZfgFAXFS/z/lEd6LJmf9HVZ1LkgYiHx5pHhV5DR16M=
 github.com/fsnotify/fsnotify v1.4.7 h1:IXs+QLmnXW2CcXuY+8Mzv/fWEsPGWxqefPtCP5CnV9I=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
+github.com/getsentry/raven-go v0.2.0 h1:no+xWJRb5ZI7eE8TWgIq1jLulQiIoLG0IfYxv5JYMGs=
+github.com/getsentry/raven-go v0.2.0/go.mod h1:KungGk8q33+aIAZUIVWZDr2OfAEBsO49PX4NzFV5kcQ=
 github.com/go-kit/kit v0.8.0/go.mod h1:xBxKIO96dXMWWy0MnWVtmwkA9/13aqxPnvrjFYMA2as=
 github.com/go-logfmt/logfmt v0.3.0/go.mod h1:Qt1PoO58o5twSAckw1HlFXLmHsOX5/0LbT9GBnD5lWE=
 github.com/go-logfmt/logfmt v0.4.0/go.mod h1:3RMwSq7FuexP4Kalkev3ejPJsZTpXXBr9+V4qmtdjCk=
@@ -78,10 +82,15 @@ github.com/lucas-clemente/quic-go v0.11.2 h1:Mop0ac3zALaBR3wGs6j8OYe/tcFvFsxTUFM
 github.com/lucas-clemente/quic-go v0.11.2/go.mod h1:PpMmPfPKO9nKJ/psF49ESTAGQSdfXxlg1otPbEB2nOw=
 github.com/marten-seemann/qtls v0.2.3 h1:0yWJ43C62LsZt08vuQJDK1uC1czUc3FJeCLPoNAI4vA=
 github.com/marten-seemann/qtls v0.2.3/go.mod h1:xzjG7avBwGGbdZ8dTGxlBnLArsVKLvwmjgmPuiQEcYk=
+github.com/maruel/panicparse v1.2.1 h1:mNlHGiakrixj+AwF/qRpTwnj+zsWYPRLQ7wRqnJsfO0=
+github.com/maruel/panicparse v1.2.1/go.mod h1:vszMjr5QQ4F5FSRfraldcIA/BCw5xrdLL+zEcU2nRBs=
+github.com/mattn/go-colorable v0.1.1/go.mod h1:FuOcm+DKB9mbwrcAfNl7/TZVBZ6rcnceauSikq3lYCQ=
+github.com/mattn/go-isatty v0.0.5/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hdxcsrc5s=
 github.com/mattn/go-isatty v0.0.7 h1:UvyT9uN+3r7yLEYSlJsbQGdsaB/a0DlgWP3pql6iwOc=
 github.com/mattn/go-isatty v0.0.7/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hdxcsrc5s=
 github.com/matttproud/golang_protobuf_extensions v1.0.1 h1:4hp9jkHxhMHkqkrB3Ix0jegS5sx/RkqARlsWZ6pIwiU=
 github.com/matttproud/golang_protobuf_extensions v1.0.1/go.mod h1:D8He9yQNgCq6Z5Ld7szi9bcBfOoFv/3dc6xSMkL2PC0=
+github.com/mgutz/ansi v0.0.0-20170206155736-9520e82c474b/go.mod h1:01TrycV0kFyexm33Z7vhZRXopbI8J3TDReVlkTgMUxE=
 github.com/minio/sha256-simd v0.0.0-20190117184323-cc1980cb0338 h1:USW1+zAUkUSvk097CAX/i8KR3r6f+DHNhk6Xe025Oyw=
 github.com/minio/sha256-simd v0.0.0-20190117184323-cc1980cb0338/go.mod h1:2FMWW+8GMoPweT6+pI63m9YE3Lmw4J71hV56Chs1E/U=
 github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=