Adds the modified xdrfile library which reads double precision...

data without doing any single-double conversion in the middle.

The original xdrfile-1.1.1 can be obtained here:
http://www.gromacs.org/Downloads

There files are modified, where some declarations of float variables
are changed to double:
xdrfile.h
xdrfile_trr.h
xdrfile_trr.c
xdr.f90 is modified to read double precision data directly...

without any precision conversion
Removes redundant double to double conversion in xdr.f90
oneTwoDecompose.f90 now uses xdr module to read trr files directly

The UI is the same.
The relevant atoms to be read must be consecutive from the beginning
in each frame of the trajectory.
Updates Makefile.ifort to compile xdr module and oneTwoDecompose