Includes adaptation by Nadav for the removal of file_input_stream:
sstables.cc used file_input_stream, which we replaced by the new
make_file_input_stream. We also couldn't make sstables.cc read either
a file_input_stream or the planned compressed_file_input_stream.
So in this patch we implement an API similar to the old "file_input_stream"
based on the new make_file_input_stream. file_input_stream now has a parent
class "random_access_reader", preparing for a future patch to support both
file_input_stream and compressed_file_input_stream in the same code - by making
all the parsers take a random_access_reader reference instead of file_input_stream.
Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
9288b360f6