base-linux: ld.lib.so loads dynamic binaries

For ARM support on N900, commit 4a9b1c6 changed the process library to
start dynamic binaries directly depending on the Linux kernel to comply
to the interp section info ("ld.lib.so"). This seems not required on
more recent platforms or kernel versions and also introduced challenging
corner cases in region handling on Linux. Therefore, this commit
restores the original behavior.
Increase quota of lwip_lx.run

See 33909779 for documentation.
demo.run: Don't delete 'launchpad.config'

Deleting the generated 'launchpad.config' file is a bad idea because in
contrast to most base platforms, on Linux, we merely create symlinks
from the 'var/run/demo/' directory to the 'bin/' directory instead of
copying the files.
base-codezero: check scons and python2.6 on prepare
base-fiasco: check byacc installation on prepare
Preserve thread-context area as early as possible
Move main bootstrap to platform-specific object

To prevent multiple execution of main-bootstrap, I moved the code to a
statically initialized object. The reason for this change is that
_main() is exeuted twice when starting dynamic binaries. Now, the object
is part of the base-common library which is linked with ld.lib.so.
base-linux: revised region management

Revised region management detects region conflicts by using _soft_
mappings per default. Overmapping is activated for population of managed
dataspaces only. For more information see header documentation of
base-linux/src/base/env/rm_session_mmap.cc.

Fixes #883.
hw: avoid mandatory function calls in assertions

ref #528
hw: no implicit uint-to-int cast in signal submit

ref #528
hw: no mandatory asserts in platform thread

ref #528
hw: no asserts in platform PD

ref #528
hw: no assertions in pagers

ref #528
hw: avoid syscall fptr. array + threads can crash

ref #528
hw: kernel configuration in dedicated header

ref #528
hw: object in extra header & asserts reviewed

ref #528
hw: scheduler in extra header & asserts reviewed

ref #528
hw: IRQ receiver in extra header & reviewed

ref #528
hw: IPC node in extra header

ref #528
base: provide class Genode::Fifo_element

ref #528