msvc-inval: Require a semicolon after DONE_MSVC_INVAL. * lib/msvc-inval.h (TRY_MSVC_INVAL, DONE_MSVC_INVAL): Wrap in a do...while(0). * lib/dup2.c (rpl_dup2): Add a semicolon after DONE_MSVC_INVAL. Suggested by Paul Eggert.