Minor nterp improvements.

Do not resolve primitive field types for iput*, sput*
before updating the interpreter cache.

Introduce and use `ArtMethod::IsStringConstructor(),
a convenience helper function where we  avoid a read
barrier for checking if the declaring class is the
`String` class.

Change one `CHECK_LE()` to `DCHECK_LE()`.

Test: testrunner.py --host --interpreter
Change-Id: I17b0409cee5321e0ca389f053da1f767d2913d08
7 files changed