on some archs, like PowerPC, char is unsigned by default. This would
result in an infinite loop on powerpc in the getopt() call in this program.
Caught by gcc with the following warning:
/usr/src/cddl/contrib/opensolaris/cmd/zstreamdump/zstreamdump.c: In function 'main':
/usr/src/cddl/contrib/opensolaris/cmd/zstreamdump/zstreamdump.c:231: warning: comparison is always true due to limited range of data type