CLEANUP: tree-wide: use VAR_ARRAY instead of [0] in various definitions

CLEANUP: tree-wide: use VAR_ARRAY instead of [0] in various definitions

Surprisingly there were still a number of [0] definitions for variable
sized arrays in certain structures all over the code. We need to use
VAR_ARRAY instead of zero to accommodate various compilers' preferences,
as zero was used only on old ones and tends to report errors on new ones.