Remove int64.h, use <inttypes.h> or <stdint.h> instead.

smartmontools/ChangeLog

smartmontools/Makefile.am

smartmontools/atacmds.cpp

smartmontools/ataidentify.cpp

smartmontools/ataprint.cpp

smartmontools/cciss.cpp

smartmontools/dev_areca.cpp

smartmontools/dev_ata_cmd_set.cpp

smartmontools/dev_intelliprop.cpp

smartmontools/dev_interface.cpp

smartmontools/dev_legacy.cpp

smartmontools/int64.h

smartmontools/knowndrives.cpp

smartmontools/nvmecmds.h

smartmontools/nvmeprint.cpp

smartmontools/os_darwin.cpp

smartmontools/os_freebsd.cpp

smartmontools/os_generic.cpp

smartmontools/os_linux.cpp

smartmontools/os_netbsd.cpp