Add an option to escape forward slash character

Squashed commit of the following:

commit 26d181059989279a79c433cedcd893b4f52e42ee
Author: Francois Chagnon <francois.chagnon@jadedpixel.com>
Date:   Tue Sep 15 21:17:34 2015 +0000

    add config options for escape_slash

commit fa282334051b16df91ca097dd7304b46f3bc7719
Author: Francois Chagnon <francois.chagnon@jadedpixel.com>
Date:   Mon Feb 9 21:09:33 2015 +0000

    add forward slash to escape character

1 files changed, 8 insertions, 2 deletions

diff --git a/java/src/json/ext/StringEncoder.java b/java/src/json/ext/StringEncoder.java
index 9d40dd3..26678ed 100644
--- a/java/src/json/ext/StringEncoder.java
+++ b/java/src/json/ext/StringEncoder.java
@@ -15,7 +15,7 @@ import org.jruby.util.ByteList;
  * and throws a GeneratorError if any problem is found.
  */
 final class StringEncoder extends ByteListTranscoder {
-    private final boolean asciiOnly;
+    private final boolean asciiOnly, escapeSlash;
 
     // Escaped characters will reuse this array, to avoid new allocations
     // or appending them byte-by-byte
@@ -37,9 +37,10 @@ final class StringEncoder extends ByteListTranscoder {
             new byte[] {'0', '1', '2', '3', '4', '5', '6', '7',
                         '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
 
-    StringEncoder(ThreadContext context, boolean asciiOnly) {
+    StringEncoder(ThreadContext context, boolean asciiOnly, boolean escapeSlash) {
         super(context);
         this.asciiOnly = asciiOnly;
+        this.escapeSlash = escapeSlash;
     }
 
     void encode(ByteList src, ByteList out) {
@@ -73,6 +74,11 @@ final class StringEncoder extends ByteListTranscoder {
         case '\b':
             escapeChar('b');
             break;
+        case '/':
+            if(escapeSlash) {
+                escapeChar((char)c);
+                break;
+            }
         default:
             if (c >= 0x20 && c <= 0x7f ||
                     (c >= 0x80 && !asciiOnly)) {