Add the actual text of the GPLv2, as the license requires us to
gznbd: use PRId64 for printing 64bit types

Gcc complains about printing these 64bit types:

gznbd.c:199:1: warning: format '%Ld' expects argument of type 'long long int',
	but argument 5 has type 'u64' [-Wformat]

Use the standard defines from inttypes.h to avoid this issue.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
gznbd: fix warning with newer zlib

When you build against newer zlib, you get a lot of warnings like so:

gznbd.c: In function 'main':
gznbd.c:87:5: warning: assignment from incompatible pointer type [enabled by default]
gznbd.c:109:5: warning: passing argument 1 of 'gzread' from incompatible pointer type [enabled by default]
In file included from gznbd.c:37:0:
/usr/include/zlib.h:1313:21: note: expected 'gzFile' but argument is of type 'struct gzFile_s **'
gznbd.c:118:9: warning: passing argument 1 of 'gzerror' from incompatible pointer type [enabled by default]

This is because the zlib API uses just gzFile everywhere, not a pointer
to a gzFile.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>