Whitespace cleanup to fix rendering nits in
src.conf(5).

Sponsored by:	The FreeBSD Foundation
Regen src.conf(5) after r275138.

Sponsored by:	The FreeBSD Foundation
Increase default and maximum callchain depths

Bump the default from 16 to 32, to accommodate kernel flamegraphs.
Bump the maximum from 32 to 128, to accommodate deep user stacks.

Reviewed by:	gnn
MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D1203