Fallocate

[mjbach]

Added graceful failure for bad CLI args. Also added fallocate support if it is found.

[fwang2]

well, there is still an issue with this implementation:
apparently, due to missing HAVE_ def, this code was never compiled.

/usr/include/fcntl.h:290:12: note: declared here
 extern int __REDIRECT (posix_fallocate, (int __fd, __off64_t __offset,
            ^
/gpfs/alpinetds/stf008/scratch/fwang2/lcio/lib/posix.c:61:13: error: too few arguments to function ‘posix_fallocate’
             *rv = posix_fallocate(*(int*)fdes, flag);
             ^
In file included from /usr/include/features.h:375:0,
                 from /usr/include/sys/stat.h:26,
                 from /gpfs/alpinetds/stf008/scratch/fwang2/lcio/lib/posix.c:1:
/usr/include/fcntl.h:290:12: note: declared here
 extern int __REDIRECT (posix_fallocate, (int __fd, __off64_t __offset,