split up 'if' statements that assign and test

split up 'if' statements that assign and test

Split 'if' statements that combine an assignment with a test.
e.g. from:

    if ((pc = imap_get_flags(&(idata->flags), pc)) == NULL)

To
    pc = imap_get_flags(&(idata->flags), pc);
    if (!pc)

This makes the statements a little easier to read and debug.