What I did was consider every OSVERSION <op> xxxx, if it is always true or false, simplify the boolean equation.

Then simplify compounds, for example (${OSVERSION} >= 900000 && ${OSVERSION} < 900021) is always true, as is (${OSVERSION} > 900002 || ${OSVERSION} < 900000 && ${OSVERSION} > 800107).

Regarding patches, when an EXTRA_PATCHES is no longer needed, I remove it, when it is always needed, I renamed it, in one case, I merged two patches.