Handle space char event correctly.
(isearch-process-search-multibyte-characters): If this-command is
not isearch-printing-char, don't read multibyte chars from
minibuffer, but just call isearch-process-search-char.
in isearch.el.
(isearch-toggle-input-method): Likewise.
(isearch-minibuffer-local-map): New variable.
(isearch-minibuffer-non-self-insert): New function.
(isearch-minibuffer-self-insert): New function.
(isearch-process-search-multibyte-characters): Read multibyte
characters from minibuffer with the keymap
isearch-minibuffer-local-map.
(isearch-input-method-title): New variable.
(isearch-toggle-specified-input-method): Set the above variables.
(isearch-toggle-input-method): Likewise.
(isearch-process-search-multibyte-characters): Give
iseach-input-method as arg to read-multilingual-string.