STYLE: Make internal-use CMake variables lowercase in KWStyle.cmake

This better follows CMake style conventions.

Change-Id: I40a4a71e4c0d11ab0c2e12ee8ef34734e9f439af
PERF: Prevent FindKWStyle.cmake from being called multiple times

Every run of FindKWStyle.cmake has the additional cost of executing
kwstyle to get its version. This change prevents FindKWStyle.cmake from
being called twice, except on a fresh configuration.

Change-Id: Ied7949bad56363f73a8e89485207536bcea097ae
BUG: Fix FindKWStyle crash when kwstyle returns empty version info

One of the dashboard machines has a version of KWStyle which returns
only an empty string or whitespace in response to "kwstyle -version". The
cause of this is unknown, but this commit will prevent FindKWStyle.cmake
from crashing in this case.

Change-Id: I093e17642d5a2ed26bb1e4be1960ce66664da787
Merge topic 'kwstyle'

9700769 BUG: Fix FindKWStyle crash when kwstyle returns empty version info
53a1cf8 PERF: Prevent FindKWStyle.cmake from being called multiple times
bc01eaf STYLE: Make internal-use CMake variables lowercase in KWStyle.cmake