Rework how various OIDs are compared in the code.

Rework how various OIDs are compared in the code.

Instead of converting the ASN1_OBJECT into a string and comparing the
strings, convert the string into an ASN1_OBJECT once and then compare
these objects with OBJ_cmp().

Makes the code a bit easier to read and removes some repetitive conversions.
With input and OK tb@