fixed g++ -gstabs+ with c++

[Michael Elizabeth Chastain]

Just FYI,

I fixed the problem in gcc HEAD where g++ -gstabs+ emits "<internal>" as
the source file name.  This fixes about 60 FAILs with gdb 5.3 and 120
FAILs with gdb gdb_6_0-branch and gdb HEAD.  This was bug gcc/10055.

There are still about 25 regressive FAILs from gcc 3.3 to gcc HEAD,
with both dwarf-2 and -gstabs+.  I will look into those soon.

There are no gdb regressions from gcc 3.3 to gcc-3_3-branch.
gcc 3.3.1 is scheduled for July 18.

It's actually not hard to fix gcc bugs that break gdb.  The gcc folks
aren't rewriting dbxout.c every week; they do other stuff, with the bad
side effect of damaging the debug info.   Their own test suite can't
catch that.

Michael C