composer: place remapper binary in the proper location
remapper: nicer code with some define
composer: now uses full path inside the repammer directory

inside the remapper directory we were using the hash of the file of
a base path, which now we use the full path.

for example the file /lib/libc-2.15.so before it was
/opt/rocks/remapper/a234scfe2824d/libc-2.15.so
now it is remapped
/opt/rocks/remapper/lib/libc-2.15.so
remapper: now it remap also the openat syscall

This is necessary since syscall is used by openmpi to load its plugin
from the directory where they are saved.