egcs-1.1/Solaris: warnings in system headers with -Wall

[papadopo at shfj dot cea dot fr (Dimitri PAPADOPOULOS-ORFANOS)]

Using egcs-1.1 with -Wall under Solaris 2.5.1, I get warnings inside
system file, like:

	/usr/openwin/include/X11/Xutil.h:843: warning: return-type of `XUnionRegion' defaults to `int'
	in function
	extern XUnionRegion(
	#if NeedFunctionPrototypes
	    Region		/* sra */,
	    Region		/* srb */,
	    Region		/* dr_return */
	#endif
	);

	/usr/openwin/include/GL/glu.h:2: warning: ignoring pragma: ignored
	in line
	#pragma ident   "@(#)glu.h      1.6  97/05/05  SMI"

Of course, these headers do contain errors (like many Sun
headers), but I have old sources that compiled without warnings
up to egcs-1.0.3a, and I don't want to change all the Makefiles.
Have more warnings been added to -Wall?
I only found the following changes documented:

     + New warning -Wno-pmf-conversion (don't warn about
       converting from a bound member function pointer to function
       pointer).

     + A flag -Weffc++ has been added for violations of some of the style 
       guidelines in Scott Meyers' _Effective C++_ books.

     + -Woverloaded-virtual now warns if a virtual function in a base
       class is hidden in a derived class, rather than warning about
       virtual functions being overloaded (even if all of the inherited
       signatures are overridden) as it did before.

     + -Wall no longer implies -W.  The new warning flag, -Wsign-compare,
        included in -Wall, warns about dangerous comparisons of signed and
        unsigned values. Only the flag is new; it was previously part of
        -W.

     + The new flag, -fno-weak, disables the use of weak symbols.