implement RecordStoreSharedDBHeader
Merge pull request #85 from mykmelez/RecordStoreSharedDBHeader

implement RecordStoreSharedDBHeader
work in progress tests of RecordStoreFile natives
Merge branch 'master' into test-record-store-file-natives
tighten up RGB read/write code in gfx
:Merge branch 'master' of github.com:andreasgal/j2me.js
basic RecordStoreFile natives tests; bug fixes to pass them; and a truncateFile impl
Merge branch 'master' into test-record-store-file-natives
ensure RecordStoreCache entry non-null; catch VM.Yield in async native; raise correct IOException
Merge pull request #88 from mykmelez/RecordStoreSharedDBHeader-error-checks

ensure RecordStoreCache entry non-null; etc.
Merge pull request #87 from mykmelez/test-record-store-file-natives

test record store file natives