fixed way to find available platforms

Since OpenCL provides a way to find the number of available platforms,
the command dispatcher now uses it.
fixed bug in ctor of option (unitialized member)
changed naming in square_matrix

naming of rows and columns was inverted
Merge pull request #92 from mavam/unstable

Provide two missing includes.
Merge branch 'unstable' of github.com:Neverlord/libcppa into unstable

Conflicts:
	src/opencl/command_dispatcher.cpp
Merge branch 'unstable' of github.com:Neverlord/libcppa into unstable
use correct msg header in reply_to
Merge branch 'unstable' of github.com:Neverlord/libcppa into unstable
changed logging from clBuildProgram

Only error is written to logfile, build log is written to cerr.
Merge branch 'unstable' of github.com:Neverlord/libcppa into unstable
added exception handling to opencl test

The opencl test provokes an execption with an incorrect opencl kernel.
accept lvalue for or_else, fixes #93
fix bug in forwarding of link operations
changed version to 0.7
Merge branch 'unstable' of github.com:Neverlord/libcppa into unstable
fixed nasty bug w/ large actor classes, fixes #88
moved uuid/mac address lookup to own units
fixed #95

this patch fixes some minor errors in the Linux implementation of
`get_mac_addresses` and `get_root_uuid`
fixed name mapping for signed char16_t, fixes #95
GCC 4.8 compatibility

the most recent changes to GCC broke some SFINAE code libcppa, this patch
solves this issue