Fixes fortran/PR35154, fortran/PR23057.

Modified from earlier submission based on comments received; sorry for 
any repetition.

It consists of three parts, two already approved, one new.  They are
grouped at FX Coudert's request; see

http://gcc.gnu.org/ml/gcc-patches/2008-02/msg01011.html

Component parts are:

1) to fortran/trans-common.c to emit .stabs debug information in the
proper scope for COMMON block variables by linking them to the function
scope rather than the global scope.  This is approved; see above link.

2) to dbxout.c and the testsuite to change how .stabs debug information
is emitted for COMMON block variables.  This was submitted and approved
in Aug. 2004 but never committed.  History is here:
(Approval):  http://gcc.gnu.org/ml/gcc-patches/2004-08/msg02475.html
(Submission): http://gcc.gnu.org/ml/gcc-patches/2004-06/msg02096.html
Now modified based on comments received.

3) to dwarf2out.c and the testsuite to change the way DWARF-2 debug 
information
is emitted for COMMON block variables in an analogous way as .stabs, 
using
DW_TAG_common_block.  This is new.  Now modified based on comments 
received.

New testsuite component updated to GCC3 license.

Bootstraps gcc, g++, objc and gfortran on powerpc-apple-darwin8.8.0,
i386-apple-darwin8.10.1, sparc64-unknown-freebsd6.0.  There are no 
testsuite
regressions against this patch for gfortran, gcc, objc or g++.  Verified
gdb functionality on i386-apple-darwin8.10.1 (-gstabs),
powerpc-apple-darwin8.8.0 (-gstabs) and sparc64-unknown-freebsd6.0 
(-gstabs and
-gdwarf-2).

OK to commit to trunk?

George Helffrich