RFR - JDK-8210718 String::detab, String::entab (CSR Review)

[Jim Laskey]

Please review the API for String::detab and String::entab. Used to expand tabs into spaces, and spaces back to tabs.

csr: https://bugs.openjdk.java.net/browse/JDK-8210718
jbs: https://bugs.openjdk.java.net/browse/JDK-8210717

Cheers,

— Jim