funcr: printing strings needs to escape contents

[thockin]

We can't just print " + str + " - it might contain (for example) newlines.

[thockin]

Ouch. Fixing this is not cheap:

before:

BenchmarkFuncrLogInfoOneArg-6            	 7090315	       848.2 ns/op
BenchmarkFuncrJSONLogInfoOneArg-6        	 6520648	       947.1 ns/op
BenchmarkFuncrLogInfoSeveralArgs-6       	 4200316	      1427 ns/op
BenchmarkFuncrJSONLogInfoSeveralArgs-6   	 3937572	      1531 ns/op
BenchmarkFuncrLogInfoWithValues-6        	 3570640	      1451 ns/op
BenchmarkFuncrJSONLogInfoWithValues-6    	 3874375	      1570 ns/op

after:

BenchmarkFuncrLogInfoOneArg-6            	 5741181	      1005 ns/op
BenchmarkFuncrJSONLogInfoOneArg-6        	 4774858	      1221 ns/op
BenchmarkFuncrLogInfoSeveralArgs-6       	 2817030	      2088 ns/op
BenchmarkFuncrJSONLogInfoSeveralArgs-6   	 2564682	      2337 ns/op
BenchmarkFuncrLogInfoWithValues-6        	 2769523	      2201 ns/op
BenchmarkFuncrJSONLogInfoWithValues-6    	 2518342	      2416 ns/op

patch:

diff --git a/funcr/funcr.go b/funcr/funcr.go
index bd834aa..c971d26 100644
--- a/funcr/funcr.go
+++ b/funcr/funcr.go
@@ -290,9 +290,7 @@ func (f Formatter) flatten(buf *bytes.Buffer, kvList []interface{}, continuing b
 			}
 		}
 
-		buf.WriteByte('"')
-		buf.WriteString(k)
-		buf.WriteByte('"')
+		buf.WriteString(strconv.Quote(k))
 		if f.outputFormat == outputJSON {
 			buf.WriteByte(':')
 		} else {
@@ -379,9 +377,7 @@ func (f Formatter) prettyWithFlags(value interface{}, flags uint32) string {
 			if i > 0 {
 				buf.WriteByte(',')
 			}
-			buf.WriteByte('"')
-			buf.WriteString(v[i].(string))
-			buf.WriteByte('"')
+			buf.WriteString(strconv.Quote(v[i].(string)))
 			if f.outputFormat == outputJSON {
 				buf.WriteByte(':')
 			} else {
@@ -467,9 +463,7 @@ func (f Formatter) prettyWithFlags(value interface{}, flags uint32) string {
 			if name == "" {
 				name = fld.Name
 			}
-			buf.WriteByte('"')
-			buf.WriteString(name)
-			buf.WriteByte('"')
+			buf.WriteString(strconv.Quote(name))
 			buf.WriteByte(':')
 			buf.WriteString(f.pretty(v.Field(i).Interface()))
 		}
@@ -498,9 +492,7 @@ func (f Formatter) prettyWithFlags(value interface{}, flags uint32) string {
 				buf.WriteByte(',')
 			}
 			// JSON only does string keys.
-			buf.WriteByte('"')
-			buf.WriteString(f.prettyWithFlags(it.Key().Interface(), flagRawString))
-			buf.WriteByte('"')
+			buf.WriteString(strconv.Quote(f.prettyWithFlags(it.Key().Interface(), flagRawString)))
 			buf.WriteByte(':')
 			buf.WriteString(f.pretty(it.Value().Interface()))
 			i++