[contrib] Bring bochs/qemu READMEs up to date with latest upstream code

contrib/bochs/README

 
 3.  Configure bochs with
       pushd bochs
-      ./configure --enable-all-optimisations --enable-pci --enable-pnic \
-                  --enable-debugger --enable-magic-breakpoints \
-		  --enable-disasm --enable-show-ips --enable-ne2000
+      ./configure --enable-all-optimisations --enable-show-ips \
+		  --enable-cpu-level=6 \
+		  --enable-pci --enable-pnic --enable-ne2000 \
+                  --enable-debugger --enable-disasm
       popd
 
 4.  Build bochs:

contrib/bochs/README.qemu

       popd
 
 9.  Start qemu
-      export SDL_VIDEO_X11_DGAMOUSE=0
       ./qemu/i386-softmmu/qemu -L qemu/pc-bios \
 			       -net nic,model=rtl8139 -net tap,ifname=tap0 \
 			       -boot a -fda ../../src/bin/rtl8139.pdsk