private void checkCallotherFixup(DocInfo doc) throws SleighException {
		CompilerSpec cspec = program.getCompilerSpec();
		PcodeInjectLibrary injectLibrary = cspec.getPcodeInjectLibrary();
		if (!injectLibrary.hasUserDefinedOp(doc.formalName)) {
			throw new SleighException("CALLOTHER_FIXUP target does not exist: " + doc.formalName);
		}
		InjectPayload payload =
			injectLibrary.getPayload(InjectPayload.CALLOTHERFIXUP_TYPE, doc.formalName);
		if (payload == null) {
			return;
		}
		if (injectLibrary.hasProgramPayload(doc.formalName, InjectPayload.CALLOTHERFIXUP_TYPE)) {
			return;
		}
		// A callother payload is allowed to override an existing core payload
		// So this check never fails, but we mark that the override is occurring
		doc.override = true;
	}
Check that the proposed callotherfixup extension targets a user-defined op
that exists.  Check if the extension would override a built-in fixup.
@param doc is info on the proposed extension
@throws SleighException if the targeted op does not exist
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/SpecExtension.java