ZipUtilsRO rewrite based on Dalvik Zip rewrite

Change the way zip archives are handled.  This is necessary to deal with
very large (~1GB) APK files, for which our current approach of mapping
the entire file falls over.

We now do the classic scavenger hunt for the End Of Central Directory
magic on a buffer of data read from the file, instead of a memory-mapped
section.  We use what we find to create a map that covers the Central
Directory only.

If the caller is interested in unpacking the file contents, we have to
do an additional file read to discover the size of the Local File Header
section so we can skip past it.

This is based on Change I745fb15abb in the dalvik tree. Both
implementations share a common ancestry, but the cost of unifying them
outweighs the benefits of wrapping C calls.

Change-Id: Iddacb50fe913917c2845708a530872d65fdbe620