top: use CPU_ZEROTICS to embrace the Nehalem logic

top: use CPU_ZEROTICS to embrace the Nehalem logic

The recently added logic dealing with "missing" tics
is mutually exclusive with logic associated with a
define called CPU_ZEROTICS.

This commit expands the use of that define to exclude
such Nehalem logic as appropriate.

It also extends programmer notes in top.h to include
an attribution for initiating the topic of potential
Nehalem type % CPU distortions, acknowledging:
  Jaromir Capik, <jcapik@redhat.com>

References
commit ce1410a51a624a91816fcc8c232c8a4d60b09638
commit 9e7dd43ab7b2e68177cefd49b3c07311ea79bc1a
commit a9041a5526eddc631b94bac86c09a47e60a3b4e1