Prefer defvar-local in MH-E

Prefer defvar-local in MH-E

* lisp/mh-e/mh-comp.el (mh-insert-auto-fields-done-local):
* lisp/mh-e/mh-e.el (mh-thread-scan-line-map)
(mh-thread-scan-line-map-stack):
* lisp/mh-e/mh-identity.el (mh-identity-pgg-default-user-id)
(mh-identity-local):
* lisp/mh-e/mh-scan.el (mh-cmd-note):
* lisp/mh-e/mh-seq.el (mh-non-seq-mode-line-annotation):
* lisp/mh-e/mh-thread.el (mh-thread-id-hash)
(mh-thread-subject-hash, mh-thread-id-table)
(mh-thread-index-id-map, mh-thread-id-index-map)
(mh-thread-subject-container-hash, mh-thread-duplicates)
(mh-thread-history): Prefer defvar-local.