Fix the final [mis]uses of iscopy.

I finally got round to going through all the dalvik/libcore/ calls to the
following routines, in cases where the final argument ("iscopy") is non-NULL:

 Get*ArrayElements
 GetStringChars
 GetStringUTFChars
 GetStringCritical
 Get*ArrayCritical

The calls in sqlite_jni.c were neither assuming that setting "iscopy" requests
a copy (a bug we've seen elsewhere), nor were they making use of the result.
I've changed these to pass NULL to make their lack of interest explicit. I've
also fixed a compiler warning (signed/unsigned comparison).

The ones in org_apache_harmony_luni_platform_OSFileSystem.cpp were genuine
errors. The author was under the misapprehension that iscopy == JNI_FALSE
implies that you do not need to call the corresponding "Release" function.
I've fixed those. (I haven't addressed the fact that readvImpl and writevImpl
differ by just one token, nor have I addressed the fact that -- in theory
though not with our current GC -- any of the GetIntArrayElements could fail.)
2 files changed