[Crash-utility] Two small issues in is_compressed_kernel()

When I was using crash 5.1.4, I found two small issues in is_compressed_kernel(). 1) For vmlinux compressed with bzip2, is_compressed_kernel() is forgetting to use basename() to a given file name before comparing it with "vmlinux", due to which specifying vmlinux by relative or absolute path lets a given vmlinux unintensionally interpreted as an unsuported format. See an attached patch, though it's very obvious. 2) is_compressed_kernel() is assuming gunzip and bunzip2 are located in /usr/bin/, but on Ubuntu they are located in /bin/, so uncompression fails on Ubuntu due to No such file error. Could you add a static or dynamic processing of detecting where binaries are located? Thanks. HATAYAMA, Daisuke