Fixes couchbaselabs#20: N1QL-like parser using participle

This commit uses participle to build a parser that will be used for XDCR's advanced filtering feature.
It is similar to N1QL with a few differences

constants.go

@@ -4,6 +4,7 @@ package gojsonsm
 
 import (
 	"fmt"
+	"regexp"
 )
 
 // Function related constants
@@ -104,3 +105,24 @@ const (
 type checkAndGetKeyFunc func(string) (bool, string)
 type funcNameType string
 type funcRecursiveIdx int
+
+// Support for pcre's lookahead class of regex
+const lookAheadPattern = "\\(\\?\\=.+\\)"
+const lookBehindPattern = "\\(\\?\\<.+\\)"
+const negLookAheadPattern = "\\(\\?\\!.+\\)"
+const negLookBehindPattern = "\\(\\?\\<\\!.+\\)"
+
+var pcreCheckers [4]*regexp.Regexp = [...]*regexp.Regexp{regexp.MustCompile(lookAheadPattern),
+	regexp.MustCompile(lookBehindPattern),
+	regexp.MustCompile(negLookAheadPattern),
+	regexp.MustCompile(negLookBehindPattern)}
+
+// Returns true if the value is to be used for pcre types
+func tokenIsPcreValueType(token string) bool {
+	for _, pcreChecker := range pcreCheckers {
+		if pcreChecker.MatchString(token) {
+			return true
+		}
+	}
+	return false
+}