function: escape_string purpose: adds \ to escape a list of characters inputs: s: The string to be escaped list=list: an array of characters to be escaped. If not set, defaults to the regex set ['[',']','{','}','\','^','$','.','|','?','*','+','(',')'] $LastChangedBy: pcruce $ $LastChangedDate: 2013-06-11 21:39:46 -0700 (Tue, 11 Jun 2013) $ $LastChangedRevision: 12513 $ $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/spdsoft/trunk/general/misc/escape_string.pro $