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/match_prev_cmd.zsh

@@ -21,18 +21,18 @@
 # `HIST_EXPIRE_DUPS_FIRST`.
 
 _zsh_autosuggest_strategy_match_prev_cmd() {
-	local prefix="${1//(#m)[\\()\[\]|*?~]/\\$MATCH}"
+	local prefix="$1"
 
 	# Get all history event numbers that correspond to history
 	# entries that match pattern $prefix*
 	local history_match_keys
-	history_match_keys=(${(k)history[(R)$prefix*]})
+	history_match_keys=(${(k)history[(R)${(b)prefix}*]})
 
 	# By default we use the first history number (most recent history entry)
 	local histkey="${history_match_keys[1]}"
 
 	# Get the previously executed command
-	local prev_cmd="$(_zsh_autosuggest_escape_command "${history[$((HISTCMD-1))]}")"
+	local prev_cmd="${history[$((HISTCMD-1))]}"
 
 	# Iterate up to the first 200 history event numbers that match $prefix
 	for key in "${(@)history_match_keys[1,200]}"; do