Removed unused 'hex_digits' constant

Found by clang's new -Wunused-const-variable

Change-Id: I426b9fb0588e6a425815b6875edfa3eb367c43cd
Removed unused constants

looks like copy-paste from vtkLine.cxx

Found by clang's new -Wunused-const-variable

Change-Id: I5307cf1d3da096378e0070d3ee8044370c1955c2
Suppress unused const variable warning

Depending on #ifs, some constants are unused;
wrapped their use in the appropriate #ifs.

Found by clang's new -Wunused-const-variable

Change-Id: Icf2c0310b00a9ae6592bbf13021e3ec066da0a7f
Merge topic 'new-clang-warnings' into master

67cf5a46 Suppress unused const variable warning
45020cc8 Removed unused constants
a1194302 Removed unused 'hex_digits' constant