[CMake] Features list should print dots every other row

[CMake] Features list should print dots every other row
https://bugs.webkit.org/show_bug.cgi?id=143832

Reviewed by Martin Robinson.

Discount private options when determining whether to print dots on a given row of the
features list. Also, simplify the logic by using only one for loop, and fix a couple errors
(inverted use of SHOULD_PRINT_DOTS, one use of the renamed variable SHOULD_PRINT_POINTS that
wasn't noticed because it only affects the first line, and use of the variable name as a
string in a conditional.)

* Source/cmake/WebKitFeatures.cmake:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@183109 268f45cc-cd09-0410-ab3c-d52691b4dbfc