Update to rscons 2.3.0

Move cross compiler to i686-elf-gcc directory.
Automatically build cross compiler using rscons subsidiary script.

.gitignore

@@ -4,10 +4,10 @@
 *.lst
 *.map
 *.bin
-/.rscons*
-/cross/.rscons*
-/cross/build*/
-/cross/*.xz
-/cross/binutils-*/
-/cross/gcc-*/
+.rscons*
+/i686-elf-gcc/build*/
+/i686-elf-gcc/*.xz
+/i686-elf-gcc/binutils-*/
+/i686-elf-gcc/gcc-*/
+/i686-elf-gcc/i686-elf-gcc/
 /build/