Simplify escaping of pattern and fix match_prev_cmd strategy

Maybe this is also a fix for #247, #248 and #258. Supersedes #267.

Testcase:
Using match_prev_cmd strategy and with these lines in history:
echo '1^'
echo '2^'
echo '1^'

type:
echo       (unexpected suggestion echo '1^' instead of echo '2^')
echo '1^1  (wrong suggestion echo '1^1echo '1^')
echo '1^#  (error "bad math expression")

src/util.zsh

@@ -1,11 +0,0 @@
-
-#--------------------------------------------------------------------#
-# Utility Functions                                                  #
-#--------------------------------------------------------------------#
-
-_zsh_autosuggest_escape_command() {
-	setopt localoptions EXTENDED_GLOB
-
-	# Escape special chars in the string (requires EXTENDED_GLOB)
-	echo -E "${1//(#m)[\"\'\\()\[\]|*?~]/\\$MATCH}"
-}