Bug report by Victor Pfautz.

ir: Use mode_is_float()/mode_is_int() instead of get_mode_sort()/->sort == irms_float_number/irms_int_number.

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

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

This way there is one central place to check that the out_count is sane.

The operation that function did was trivial, not abstracting it avoids repeated
get_irn_edge_info() calls in some cases.

This fixes several tests on ARM.