Reverted the temporary debugging commits in r82755, so test_float is now crashing again on that buildbot.

I've made yet another temporary commit (r82756) to get the configure script to tell me what gcc version is being used on that machine.  Once I've got that info, I can have a go at reproducing this locally.  If that fails, I'll create a branch and try to debug the buildbot remotely via repeated test runs on that branch.

... and the results from the configure script are in: it's an experimental prerelease version of gcc!  This makes me even more suspicious that it's a compiler bug.

checking gcc version... Using built-in specs.
COLLECT_GCC=/usr/lib/gcc-snapshot/bin/gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc-snapshot/libexec/gcc/i686-linux-gnu/4.6.0/lto-wrapper
Target: i686-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 20100702-0ubuntu1' --with-bugurl=file:///usr/share/doc/gcc-snapshot/README.Bugs --enable-languages=c,ada,c++,java,fortran,objc,obj-c++ --prefix=/usr/lib/gcc-snapshot --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --disable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-plugin --enable-gold --with-plugin-ld=ld.gold --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.6-snap/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.6-snap --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.6-snap --with-arch-directory=i386 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-targets=all --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=yes --build=i686-linux-gnu --host=i686-linux-gnu --target=i686-linux-gnu
Thread model: posix
gcc version 4.6.0 20100702 (experimental) [trunk revision 161740] (Ubuntu 20100702-0ubuntu1)