Run ldconfig on make install as it is required to use the plugins compre...

...ssd and zlibvalid.

This fixes the warnings:

 *WARNING: Failed to load plugin module 'compressd': libcompress42.so: cannot open shared object file: No such file or directory*

 *WARNING: Failed to load plugin module 'zlibvalid': libtinfl.so: cannot open shared object file: No such file or directory*

In combination with issue #32 this make binwalk stop working generally.

HTH,
Thomas