This commit defines all exit codes in one place in the exitcodes
package.
Also, it adds a test to verify the exit code on incorrect
password, which is what SiriKali cares about the most.
Fixes https://github.com/rfjakob/gocryptfs/issues/77 .
Misspell Finds commonly misspelled English words
gocryptfs/internal/configfile/scrypt.go
Line 41: warning: "paramter" is a misspelling of "parameter" (misspell)
gocryptfs/internal/ctlsock/ctlsock_serve.go
Line 1: warning: "implementes" is a misspelling of "implements" (misspell)
gocryptfs/tests/test_helpers/helpers.go
Line 27: warning: "compatability" is a misspelling of "compatibility" (misspell)
