Potential regression (Jan. 13): stringWrite with Java8

Significant drop of performance in stringWrite with Java8 from commit 881062f352 to 5d9d8748b6 . It only involves strings not so long (128 or 4).

stringWrite.128.ascii(Java8) baseline=1089.107756 current_value=754.52452
stringWrite.128.chinese(Java8) baseline=504.244575 current_value=295.358989
stringWrite.128.russian(Java8) baseline=655.582639 current_value=421.030188
stringWrite.4.chinese(Java8) baseline=9598.791964 current_value=6627.929927
stringWrite.4.russian(Java8) baseline=11070.666415 current_value=8289.95767