It turns out even quite recent gdb (7.1) reportedly does not
support DWARF4, moreover while the produced binaries are smaller,
faster and make gdb initially use less memory, this quickly ceases
to the case as soon as one actually does anything in gdb.
Presumably the DWARF4 handling in current gdb is very inefficient
(http://sourceware.org/bugzilla/show_bug.cgi?id=13498).

This reverts commit 5214f784.

Conflicts:

	solenv/gbuild/platform/WNT_INTEL_GCC.mk
	solenv/gbuild/platform/unxgcc.mk