Using StringBuilder in StringUtils#capitalize method

StringBuffer is synchronized which is slower and should be replaced with
StringBuilder according to its Javadoc.

Change-Id: If4d4a5a49da289ded34bbec97132ab7636b937cc
Signed-off-by: Lars Vogel <Lars.Vogel@vogella.com>

org.eclipse.jgit/src/org/eclipse/jgit/util/StringUtils.java

@@ -121,7 +121,7 @@ public final class StringUtils {
 		if (str == null || (strLen = str.length()) == 0) {
 			return str;
 		}
-		return new StringBuffer(strLen)
+		return new StringBuilder(strLen)
 				.append(Character.toTitleCase(str.charAt(0)))
 				.append(str.substring(1)).toString();
 	}