We need to be explicit about I/O as it cannot be simply repeated. A response
from the daemon will come eventually, either success or failure.

Previously, an ES was created for each destination in each read or write.
Creating and freeing these ES is costly. Also, these ESs had separate pools,
which is bad practice. Multiple ESs work on a single pool. The ABT_sched
decides which ULT or Tasklet is run by which ES at any time.

This change does also reduce CPU load as library IO RPC calls used CPU time
while waiting for the response.

ADA-FS's statfs will fill the struct mostly with rough estimations.
It is not supposed to return accurate data but "some" data for applications to work

Added lseek64 syscall and used file flags properly

Preload lib: RPC/IPC Mercury/Margo environments are only initialized if the mountdir path is used by the application
For that, the daemon writes the mountdir (it was started with) to a configurable path to disk.
The libraries read this value and only the process that uses part of this path will actually trigger the environment initialization.
This forbids prior behavior where applications initialize the whole environment numerous times, although unused.
For example, any MPI program will spawn multiple processes, all with the LD_PRELOAD environment variable set.

- should permissions be checked when access() is called or discarded. Default off
//#define CHECK_ACCESS
- If access permissions should be checked while opening a file. Default off
//#define CHECK_ACCESS_DURING_OPEN
- If disabled, a file or directory is always presumed to be there (even if it is not). No check is executed. Default on.
#define DO_LOOKUP

- Add: adafs_access, open with check if object exists
- Add: root metadentry to database of each node
- Modified: Open, unlink, mkdir, rmdir and combined their functionality to "create node" and "remove node"