Also choose a signed integer type which is more typical for offsets.

This adds two builtin kinds, ir_bk_va_start and ir_bk_va_arg. va_arg Builtins
are lowered in the lower_builtins pass with a function provided by the backend,
whereby most architectures can use be_default_lower_va_args. va_start Builtins
are lowered in the backend.

Note: This commit breaks all backends except for IA32. SPARC and AMD64 are
implemented in later commits. The ARM backend previously miscompiled variadic
functions, and will now throw a proper error.

create_compilerlib_entity() does it already, so it is not necessary to do it again in replace_with_call().

* No \n at end; panic() adds one
* No punctuation mark at end
* Lowercase first letter

You now only have to specify 1 type and the size of the access instead
of 2 types. Also cleaned up some code/comments in the process.

- It was only available in the ia32 backend and broken there. As the
  feature is rarely used, I remove it for now instead of going through
  the trouble of fixing it.

This can be used to effectively test aliasing in libfirm.

Deduce the mode automatically from the given entity.

This removes the strange entity/type duality and we get rid of union symconst_symbol.

It has been empty for nearly all systems. People who used to put stuff
in config.h can still create a config.h on their own and inject
-include (gcc) or /FI (msvc) into their CPPFLAGS.

The builtin can be used to generate fast code for unsigned division by constant.

Code generation is supported for the IA32 and the SPARC backend.
Since our ARM backend currently has no Add with Carry instruction,
the builtin is currently not supported on Arm.
The same holds for the AMD64 backend, which does not support a division yet.

Just state the copyright and the project the files belong to. You can
then find the COPYING file for the whole project.

irgmod: Pass the new inputs to turn_into_tuple() instead of initialising them with Bad and setting them afterwards.