Rewrap some long lines in the toplevel Makefile

Only rewrap long lines in make scope; long lines in shell scope
are untouched.

We are inconsistent about whether continuation lines for listing
the dependencies of a target are indented by one or two tabs,
which this commit does not fix.

Change-Id: I2e438a0f42faa2ef7922d2c3b143e14bc82de826
Reviewed-on: http://gerrit.openafs.org/11178
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: D Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>