Fix xxhash symbol conflict by using namespace

Author: guileen

parser/parser.go

@@ -1,7 +1,7 @@
 package parser
 
 /*
-#cgo CFLAGS: -Iinclude -Iinclude/postgres -g -fstack-protector -std=gnu99 -Wno-unknown-warning-option
+#cgo CFLAGS: -Iinclude -Iinclude/postgres -g -fstack-protector -std=gnu99 -Wno-unknown-warning-option -DXXH_NAMESPACE=PG_QUERY_
 #cgo windows CFLAGS: -Iinclude/postgres/port/win32
 #cgo LDFLAGS:
 #include "pg_query.h"
@@ -290,4 +290,4 @@ func HashXXH3_64(input []byte, seed uint64) (result uint64) {
 	result = *(*uint64)(unsafe.Pointer(&res))
 
 	return
-}
+}