goyacc: fix unstability of generated parser.go (pingcap#9)

Makefile

@@ -1,4 +1,4 @@
-.PHONY: all parser goyacc clean
+.PHONY: all parser clean
 
 ARCH:="`uname -s`"
 MAC:="Darwin"
@@ -9,7 +9,7 @@ all: parser.go
 parser.go: parser.y
 	make parser
 
-parser: goyacc
+parser: bin/goyacc
 	bin/goyacc -o /dev/null parser.y
 	bin/goyacc -o parser.go parser.y 2>&1 | egrep "(shift|reduce)/reduce" | awk '{print} END {if (NR > 0) {print "Find conflict in parser.y. Please check y.output for more information."; exit 1;}}'
 	rm -f y.output
@@ -23,9 +23,9 @@ parser: goyacc
 		/usr/bin/sed -i "" 's/yyEofCode/yyEOFCode/' parser.go; \
 	fi
 
-	@awk 'BEGIN{print "// Code generated by goyacc"} {print $0}' parser.go > tmp_parser.go && mv tmp_parser.go parser.go;
+	@awk 'BEGIN{print "// Code generated by goyacc DO NOT EDIT."} {print $0}' parser.go > tmp_parser.go && mv tmp_parser.go parser.go;
 
-goyacc:
+bin/goyacc: goyacc/main.go
 	go build -o bin/goyacc goyacc/main.go
 
 clean:

goyacc/main.go

@@ -222,7 +222,15 @@ func (s symsUsed) Less(i, j int) bool {
 		return false
 	}
 
-	return strings.ToLower(s[i].sym.Name) < strings.ToLower(s[j].sym.Name)
+	caseFoldedCompare := strings.Compare(strings.ToLower(s[i].sym.Name), strings.ToLower(s[j].sym.Name))
+	if caseFoldedCompare < 0 {
+		return true
+	}
+	if caseFoldedCompare > 0 {
+		return false
+	}
+
+	return s[i].sym.Name < s[j].sym.Name
 }
 
 func main1(in string) (err error) {