In C++17 `register` keyword was removed. Current gcc 8.1.0 produces
following warning if `-std=c++17` flag is used:
warning: ISO C++17 does not allow 'register' storage class specifier
GCC almost completely ignores `register` keyword, with rare exception of
`-O0` when additional copy from/to stack may be generated.
For simplicity of the codebase it is better to just remove this
problematic keyword where it is not strictly required.
Signed-off-by: Khem Raj <firstname.lastname@example.org>