[tlbuild] proposed change to xdvi.c

[Nelson H. F. Beebe]

Today, I got a successful build of a texlive-20120414 snapshot on
GNU/Linux IA-64, and on testing it, got this warning

xdvi-xaw(5977): unaligned access to 0x60000fffffc7eb14, ip=0x20000000003cf500

Some debugger work tracked down the cause: in file
source/texk/xdvik/xdvi.c, at line 3303 the declaration

	xuint32 data;

needs to be changed to

	double data;	/* was xuint32, but need 8-byte alignment on some systems */

because &data gets passed into the X11 library via function
XChangeProperty() and is dereferenced there as an 8-byte value.  Its
contents are not examined in xdvi.c, so this change is harmless for
all systems.

The unaligned access warning indicates that the kernel did a run-time
fixup, and causes significant performance loss on IA-64 when there are
many such exceptions.


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