CMakeLists.txt: Only install cppad_colpack.cpp when colpack_prefix is specified.
CMakeLists.txt: Only install cppad_colpack.cpp when colpack_prefix is specified.

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