support boost context 1.51
remove fiber::m_size, not needed
add valgrind stack tracking
add cmake check for valgrind.h
fix build when no boost_context available
fix compile error when using boost 1.52
add configure option to disable qt examples only
maintenance & type_list interface changes

the type_list interface changed and the class itself no longer has
any members, tl_size<>, tl_head<>, etc. must be used instead;
these "template functions" also work with any variadic template class;
this patch also changes some code parts to be more consistent with
libcppa's coding style and naming convention
new class: int_list

this class provides a convenient way to access int parameter packs
in the same way as type_list does for type parameter packs
don't use std::begin/std::end in memory interface

the use of std::begin/std::end has reported to cause ambiguity errors
on some compilers
cleaned up code in producer_consumer_list
better debug output and new requirement
optimized loop and added requirements
Fix a potential linker problem.

The problem occurs when Boost and the compiler have the same default
installation path. In this case, CMake tries to be smart during link time and
replace the absolute path of the shared library with -l<lib>. With both
system-wide and user-provided installations, this can cause CMake to pick up
the wrong version of the library. Adding an explicit -L flag to the linker
command helps.
Merge pull request #85 from mavam/topic/build-harness

Fix a potential linker problem.
Merge branch 'master' into unstable
Merge branch 'master' of https://github.com/toffaletti/libcppa into unstable
reduced #ifdef statements to minimum
solved bug in chaining impl, fixes #83
complement documentation of intrusive ptr
fixed chaining for exited context-switching actors
more output in test__spawn