reduce_index.py: exclude more simple prepositions.
reduce_index.py: exclude more simple prepositions.

wegamekinglc/CppAD,kaskr/CppAD,kaskr/CppAD,wegamekinglc/CppAD,kaskr/CppAD,kaskr/CppAD,wegamekinglc/CppAD,kaskr/CppAD,wegamekinglc/CppAD,wegamekinglc/CppAD