validate: check binary signatures, handle missing libraries
validate: check binary signatures, handle missing libraries

move the individual validates into a function.

h.New() panics if the function is not compiled in, have the function
recover from that

Keep track of what hashes could be tried and what were tried. Print out the
ones we actually tried at the end.

The signature file might be binary; if the signature fails, try its contents
as a binary signature.

Signed-off-by: Ronald G. Minnich <f569d0af9a3481c4007b95c7180d6c41009f2513@google.com>

hugelgupf/u-root,rminnich/u-root,u-root/u-root,hugelgupf/u-root,rminnich/u-root,rminnich/u-root,GanShun/u-root,u-root/u-root,rminnich/u-root,u-root/u-root,GanShun/u-root,hugelgupf/u-root,hugelgupf/u-root,GanShun/u-root