Support FORMAT(I<1+2>) (constant variable-FORMAT
        expressions):
        * bad.def (FFEBAD_FORMAT_VARIABLE): New diagnostic.
        * std.c (ffestd_R1001rtexpr_): New function.
        (ffestd_R1001dump_, ffestd_R1001dump_1005_1_,
        ffestd_R1001dump_1005_2_, ffestd_R1001dump_1005_3_,
        ffestd_R1001dump_1005_4_, ffestd_R1001dump_1005_5_,
        ffestd_R1001dump_1010_2_, ffestd_R1001dump_1010_3_,
        ffestd_R1001dump_1010_4_, ffestd_R1001dump_1010_5_):
        Use new function instead of ffestd_R1001error_.
        * stb.c (ffestb_R10014_, ffestb_R10016_, ffestb_R10018_,
        ffestb_R100110_): Restructure `for' loop for style.
Change from Craig.

From-SVN: r18181