modified version of the old one which don't allow '.'
    in #define Identifiers. This allow correctly preprocess
    the following code in *.S

        #define SRC(y...)               \
        9999: y;                        \
        .section __ex_table, "a";       \
        .long 9999b, 6001f      ;       \
        // .previous

        SRC(1: movw (%esi), %bx)
        6001:

    A test included.