fix whitespace and a compiler warning in factor_lehman.c
fix whitespace and a compiler warning in factor_lehman.c

dsroche/flint2,dsroche/flint2,fredrik-johansson/flint2,jpflori/flint2,jpflori/flint2,fredrik-johansson/flint2,dsroche/flint2,wbhart/flint2,wbhart/flint2,wbhart/flint2,jpflori/flint2,fredrik-johansson/flint2,dsroche/flint2,jpflori/flint2