[CODEC-276] Reliance on default encoding in MurmurHash2 and MurmurHash3.

Update Javadoc with fix from Alex Herbert.

Author: garydgregory

src/main/java/org/apache/commons/codec/digest/MurmurHash2.java

@@ -137,7 +137,10 @@ public static int hash32(final byte[] data, final int length) {
 
     /**
      * Generates a 32-bit hash from a string with a default seed.
-     * The string is converted to bytes using the default encoding.
+     * <p>
+     * Before 1.14 the string was converted using default encoding. 
+     * Since 1.14 the string is converted to bytes using UTF-8 encoding.
+     * </p>
      * This is a helper method that will produce the same result as:
      *
      * <pre>
@@ -248,7 +251,10 @@ public static long hash64(final byte[] data, final int length) {
 
     /**
      * Generates a 64-bit hash from a string with a default seed.
-     * The string is converted to bytes using the default encoding.
+     * <p>
+     * Before 1.14 the string was converted using default encoding. 
+     * Since 1.14 the string is converted to bytes using UTF-8 encoding.
+     * </p>
      * This is a helper method that will produce the same result as:
      *
      * <pre>

src/main/java/org/apache/commons/codec/digest/MurmurHash3.java

@@ -237,7 +237,10 @@ public static int hash32(final byte[] data) {
 
     /**
      * Generates 32-bit hash from a string with a default seed.
-     * The string is converted to bytes using the default encoding.
+     * <p>
+     * Before 1.14 the string was converted using default encoding. 
+     * Since 1.14 the string is converted to bytes using UTF-8 encoding.
+     * </p>
      * This is a helper method that will produce the same result as:
      *
      * <pre>
@@ -755,7 +758,10 @@ public static long[] hash128x64(final byte[] data) {
 
     /**
      * Generates 128-bit hash from a string with a default seed.
-     * The string is converted to bytes using the default encoding.
+     * <p>
+     * Before 1.14 the string was converted using default encoding. 
+     * Since 1.14 the string is converted to bytes using UTF-8 encoding.
+     * </p>
      * This is a helper method that will produce the same result as:
      *
      * <pre>