I/O related performance benchmarks

Matthias Vogelgesang a94994dcd5 Add test to measure modification time %!s(int64=9) %!d(string=hai) anos
hdf5 a94994dcd5 Add test to measure modification time %!s(int64=9) %!d(string=hai) anos
tiff dfbfe3b766 Unify and simplify flags for older machines %!s(int64=9) %!d(string=hai) anos
.gitignore d442381b2a Build hdf5perf and ignore executable %!s(int64=9) %!d(string=hai) anos
Makefile 9407467baa Fix CFLAGS once and for all %!s(int64=9) %!d(string=hai) anos
c.mk 9407467baa Fix CFLAGS once and for all %!s(int64=9) %!d(string=hai) anos