readelf: match GNU readelf formatting

GNU readelf emits a blank line before, and uses single quotes around the
symbol table name, in each "Symbol table 'name' contains ## entries"
header.

Reviewed by: markj
MFC after: 3 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D37746

(cherry picked from commit 766145637dd5f1316c2ac4a20956e1b17bf8df42)