Merge pull request #215 from zhang-jingwang/master

Fix a build error with OpenMPI v1.4.3
Merge branch 'master' of github.com:plfs/plfs-core into 2.4dev
Fix a build error with OpenMPI 1.4.x

The function ADIOI_PLFS_Feature() shouldn't be defined when
compiling PLFS with OpenMPI 1.4.x.
re-added 1-n information to plfsrc.5in that was accidently removed in an earlier merge
Merge branch '2.4dev' of github.com:agtorre/plfs-core into 2.4dev
Merge pull request #222 from agtorre/2.4dev

Merging of other branches + fix to plfsrc.5in
Add two APIs to manage the internal cache of small file mode

plfs_flush_writes() will flush all the buffers related to the dir,
so that all the changes to regular files in this directory made by
this process are written to backend file systems.

plfs_invalidate_read_cache() will drop all the caches related
to a directory so that later operations will get the latest info
about its regular files from backend file systems.

Together they can provide a consistency semantic for small file
mode as following:
Process A:
    plfs_write(); plfs_close(); plfs_flush_writes(); Barrier();
Process B:
    Barrier(); plfs_invalidate_read_cache(); plfs_open(); plfs_read();
Then the plfs_read() in process B can see the data written by
process A.