Using proper malloc() while writing MSEED data.

The datasamples pointer in writeMSEED() is now filled with a proper
malloc call and not the old and hackish resizing approach. Now also runs
on Python 2.7.4. Fixes #551.

Also changed the MSTraceGroup to a simple MSTrace as it is only used one
trace at a time.

Requires recompilation of the shared obspy.mseed library.
Fixing confusion of numpy.string_ dtypes.

test_writeAndReadDifferentEncodings() now works across different NumPy
versions. Fixes #552.

Conflicts:
	obspy/mseed/tests/test_mseed_reading_and_writing.py
Bugfix for waveform plotting.

There a slight error in the data binning. It always occurred but only
manifested for certain data lenghts. Also added a test for it.
stream.plot(): More fixes

Found another sample count that messes with the binning. This should
solve the issue.
fixing a failing import
all public C methods need to be listed in .def file for win
fixing incorrect entry point for obspy.db features
fixes #489

Conflicts:
	obspy/core/util/xmlwrapper.py
fixing download_url for dev version via easy_install
Small bugfix for blockette 60 initialization.
fixes #554
Replacing the numpy views with true type casts.

Views do not change the underlying data and thus do not work with
custom C code that expects raw data of the correct type.

Conflicts:
	obspy/core/tests/test_stream.py
adding missing import
adding a missing import
remove darwin_compiler_fixup (missing in newer python 2.7
reverting commit 0ef60b8 as xml_doc gets closed too

Conflicts:
	obspy/core/util/xmlwrapper.py
Making setup.py work with OSX compilers.

The clang compiler shipping with newer OSX versions does not honor the
LIBRARY_PATH variable and thus cannot find the gfortran libraries. This
adds a workaround. Works with OSX 10.7 and the latest official XCode
clang version. Also tested with a local gcc installation. Works with
Python 2.6.8 and 2.7.5. Tested with NumPy 1.6.2 and 1.7.1 for each. All
other dependencies where the latest versions from pypi.
Changelog for 0.8.4
Merge pull request #583 from obspy/rc2_0.8.4

Prepare 0.8.4 -- 0.8.3 plus important bugfixes