amd64: Remove duplicate assert.

get_tarval_uint64() checks the same.
execfreq: Remove unnecessary fabs().

The result of gs_matrix_gauss_seidel() never is negative.
let backends announce whether they support PIC
move beabi/PIC code into ia32 backend

The code was only working on ia32 and contains several ia32 specific
bits, so keep it in the ia32 backend for now. At least the amd64 backend
will require a different implementation of PIC.
ia32: remove odd nonexisting SymConst transformation
simplify bemain callbacks

before_abi() callback was removed, you can simply put that code at the end
of the init() callback. custom_abi flag was removed, if a backend needs the
be_abi_introduce() stuff (formerly custom_abi == false) then it can call
it at the end of the init() callback.
cleanup, use C99
push usage of assure_irg_properties/confirm_irg_properties in backend
bemain: some small cleanups
fix incorrect usage of current_ir_graph
ia32: simplify 64bit lowering

Use the same style as the SPARC 64bit lowering, making the additional
handle_intrinsics step unnecessary now.
change intrinsic lowering API

- You can now construct the lookup table separately and perform the
  lowering selectively on irgs (instead of the whole program at once)
  while reusing the lookup table.
- Simplified API a bit.
- Remove i_mapper_RuntimeCall. All users are simpler by doing the
  transformations directly instead of filling in runtime_rt
  structures...
use float_arithmetic mode when lowering fabs calls
be: merge init_graph() and prepare_graph() callbacks into one
be: add convenience function for flagtest+dump
be: simplify verify code
be: merge finish_graph() and emit() callback

- The backends can simply perform the finish_graph() steps in the emit()
  phase.
bemain: fix strange statev output
amd64: add missing be_add_missing_keeps()
amd64: fix be_IncSP emitter