* mu4e-utils,mu4e-log: some cleanup, small additions:

- move logging vars to mu4e-utils
  - some typos fixed
  - add mu4e-ask-maildir-check-exists, which is like mu4e-ask-maildir, but
    checks that the maildir exists, if not, ask the user

emacs/mu4e-vars.el

@@ -309,12 +309,6 @@ in which case it will be equal to `:to'.)")
 viewed in view mode.")
 
 
-(defvar mu4e-log-max-lines 1200
-  "*internal* Last <n> number of lines to keep around in the buffer.")
-
-(defconst mu4e-log-buffer-name "*mu4e-log*"
-  "*internal* Name of the logging buffer.")
-
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; our handlers funcs