Remove version numbering from the pkg-config file.  We don't create
include files that are named by version.  Programs linked using -lwiredtiger
will follow the symlink to wiredtiger-a.b.c.so, so their referred library
name is forever stamped as wiredtiger-a.b.c.so, which won't conflict
even when we ship wiredtiger-a.b.d.so .
Refs #1458.
Merge pull request #1511 from wiredtiger/pkg-config

Remove version numbering from the pkg-config file.