Use typed arrays instead of normal JS arrays to back files in the MEMFS filesystem for improved performance, especially when backing to IDBFS.
Convert MEMFS files to typed arrays before storing to IDBFS for better IDBFS performance. Add testing for -s MEMFS_APPEND_TO_TYPED_ARRAYS=1 option.
Fix test_fwrite_0 syntax error in s_ modes after previous change.
Fix MEMFS.getFileDataAsTypedArray to be strict and not return unused capacity padding bytes.
Simplify typed array creation code in MEMFS.
Merge pull request #2406 from juj/typedarray_memfs

Typedarray memfs