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.