Fix CRP188 equal operator

[sacereda]

CRP:188::operator== should be const.
MSVC complains when trying to do something like:

CRP188 r0(0);
CRP188 r1(0);
bool b = r0 == r1;

error C2666: 'CRP188::operator ==': overloaded functions have similar conversions
ajantv2\includes\ntv2rp188.h(67): note: could be 'bool CRP188::operator ==(const CRP188 &)'
ajantv2\includes\ntv2rp188.h(67): note: or 'bool CRP188::operator ==(const CRP188 &)' [synthesized expression 'y == x']
note: while trying to match the argument list '(CRP188, CRP188)'