* Also only use the necessary number of bits.
* Improve its comment.

* Classify ',' as "no support" instead of "invalid".
* Ignore '!' and '?'.

* GCC does this, too.
* This is sensible, because they apply to all alternatives of a multi-alternative constraint.
* This simplifies the implementation and makes some flags obsolete.

This also renders get_irg_n_anchors() obsolete, so remove it.

This is useful for backend development.

* Use enum instead of magic number
* Do not unnecessarily lose debug information

* Provide a function for a full Immediate (entity + constant) and one for just a constant
* Place all immediates in the start block
* This slightly reduces the inconsistency, that some constant-only Immediates had no_pic_adjust set

l_{Shl,Shr,Sar}Dep are long gone.
So there are no shift operations with a third input (dependency) anymore.

It only worked, if a single value, which was at TOS, should be popped.