unit-at-a-time option causes incorrect line numbers in warnings

[David Edelsohn]

	unit-at-a-time also inhibits warnings for gcc.dg/warn-1.c as has
appeared on regression results for all platforms.

rios0 109> ./xgcc -B./ -O3 -S /gcc/dje/src/gcc/testsuite/gcc.dg/warn-1.c
rios0 110> ./xgcc -B./ -O3 -S -fno-unit-at-a-time /gcc/dje/src/gcc/testsuite/gcc.dg/warn-1.c
In file included from /gcc/dje/src/gcc/testsuite/gcc.dg/warn-1.c:15:
/gcc/dje/src/gcc/testsuite/gcc.dg/warn-1.c:8: warning: passing arg of `foo' makes integer from pointer without a cast

David