Low-level C libraries for manipulating GROMACS XTC and TRR files. This code
is derived from xdrfile-1.1.4, available at

http://www.gromacs.org/Developer_Zone/Programming_Guide/XTC_Library
ftp://ftp.gromacs.org/pub/contrib/xdrfile-1.1.4.tar.gz

These files are licensed under a BSD 2-clause license, and copyright
Erik Lindahl, David van der Spoel, Robert T. McGibbon.

Changes from upsteam's xdrfile-1.1.4 include:
 - More descriptive error strings printed inside xdrfile.c
 - Fix for a segfault on malformed xtc files inside xdrfile_decompress_coord_float (https://github.com/mdtraj/mdtraj/pull/607, https://mailman-1.sys.kth.se/pipermail/gromacs.org_gmx-developers/2014-September/007942.html)
 - Addition of read_xtc_nframes function in xdrfile_xtc.c
 - Addition of read_trr_nframes function in xdrfile_trr.c
 - Bugfix in do_trnheader to return the appropriate error code when reading magic, and properly check the value of the magic in xdrfile_trr.c
 - Bugfix of float exception (divide by zero) in xdrfile.c, see https://github.com/SimTk/mdtraj/issues/616
