libc: print 'not implemented' in pthread stubs

Print a 'not implemented' debug message if one of the libc-internal
pthread dummy functions gets called.

Fixes #730.
libc_lwip_nic_dhcp: provide '/etc/resolv.conf'

With this patch, the 'libc_lwip_nic_dhcp' plugin provides the DNS server
address acquired by lwIP via DHCP in the file '/etc/resolv.conf'.

This feature can be disabled from the config file:

<libc resolv="no" />

The static network interface configuration attributes are now also a part
of the '<libc>' config node:

<libc ip_addr="..." netmask="..." gateway="..." />

Fixes #731.
libc_fs: don't throw exception in 'open()'

Fixes #729.
ldso: increase 'MEM_SIZE' in 'mmap()'

Fixes #728.
core: preserve more memory

core needs to preserve more memory when built with -O0 for the 64-bit
'linux_x86' platform

Fixes #727.
mmio: fix bug in read/write array items

Fix #668
Update Qt to version 4.8.4

Fixes #703.
LWIP: Use LWIP_SO_RCVBUF instead of LWIP_RCVBUF

The name of this option has changed

Issue #382
Remove obsolete Fiasco UX framebuffer driver
Unify framebuffer driver binary names (fix #720)

Introduce 'framebuffer' SPEC variable to distinguish hardware framebuffer
drivers furthermore from the SDL framebuffer driver used by Genode/Linux.
Implement i.MX53 gpio driver
Unify GPIO driver binary names to 'gpio_drv'

Introduce 'gpio' SPEC variable to easily support a corresponding driver within
run scripts.
Implement i.MX53 framebuffer driver
Implement platform driver for i.MX53 platform

Move clock and reset controller functionality out of framebuffer driver
into platform driver.
Rework i.MX53 framebuffer driver

* Simplify IPU register definitions using templates
* Distinguish between i.MX53 QSB and SMD board in driver
* Support IPU specific overlay mechanism by framebuffer session extension
Double buffering for i.MX53 fb driver (fix #721)

Enable optinal support for double buffering in the i.MX53 framebuffer
driver. This prevents flickering in certain scenarios, where applications
directly render in the framebuffer dataspace given by the driver.
Remove superfluous pl11x target.mk file (fix #722)