Remove some trailing whitespace

Remove some trailing whitespace

x509_prn.c r1.6 changed the output of 'openssl -in foo.pem -noout -text'
by removing trailing whitespace from non-critical certificate extensions.
Committing the difference now to reduces noise in an upcoming diff.

There's some trailing whitespace remaining. That's because we try to print
a BMPString in an User Notice's Explicit Text with "%*s". That doesn't work
so well with an encoding full of NULs...