unwind-dw2-fde.c change breaks AIX

[David Edelsohn]

>>>>> Geoff Keating writes:

Geoff> I don't know what would be better on AIX, to have the '.' or not to
Geoff> have it.  I suspect any change will break something.

	That doesn't really help us decide how to address the problem. :^)

	The uses of __USER_LABEL_PREFIX__ do not seem to handle much
beyond "" and "_" (see toplev.c and cppinit.c).  config/rs6000/sysv4.h
uses "%U" to print the __USER_LABEL_PREFIX__, but rs6000.h and aix.h never
refer to it.  aix.h overrides ASM_OUTPUT_LABELREF in default.h which uses
it.  I do not see how the definition is doing much good.  Punting this
decision to gcc-3.1 is not going to make any difference.

David