BFD will soon be the sole user of accross.m4 in uberbaum and I would 
like to be able to delete it.

BFD includes it for AC_COMPILE_CHECK_SIZEOF and that macro's 
functionality has been superceded by autoconf 2.59's AC_CHECK_SIZEOF.

This simple patch replaces those occurences.

Tested with i686-pc-cygwin native and i686-pc-gnu-linux to 
powerpc-unknown-elf newlib cross.  No changes in stripped binaries with 
this patch.

OK to install?