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/strategies/default.zsh

@@ -7,19 +7,9 @@
 #
 
 _zsh_autosuggest_strategy_default() {
-	# Reset options to defaults and enable LOCAL_OPTIONS
-	emulate -L zsh
-
-	# Enable globbing flags so that we can use (#m)
-	setopt EXTENDED_GLOB
-
-	# Escape backslashes and all of the glob operators so we can use
-	# this string as a pattern to search the $history associative array.
-	# - (#m) globbing flag enables setting references for match data
-	local prefix="${1//(#m)[\\*?[\]<>()|^~#]/\\$MATCH}"
+	local prefix="$1"
 
 	# Get the history items that match
 	# - (r) subscript flag makes the pattern match on values
-	suggestion="${history[(r)$prefix*]}"
-
+	suggestion="${history[(r)${(b)prefix}*]}"
 }