aborting C gse2 decompression when n_samps == 0

reading gse2 files with n_samps = 0 will directly lead to segmentation
faults. Therefore, raising an Exception if that happens (see #538).
Even better handling for corrupt gse2 header.

Let the checksum detect the error when applied to a zero length array,
that's what a checksum is for, see #538.
correcting test file name

see #538
Merge pull request #538 from mbyt/538

obspy.core.read() no return from function when GSE2 chksum is wrong
Update of the SEEDManual_V2.4.pdf to the latest version of August 2012
Merge pull request #577 from bonaime/master

Update of the SEEDManual_V2.4.pdf to the latest version of August 2012
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.
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
arclink: check times in getInventory on channel level instead of
location level (i.e. on downmost level). this can help with faulty
location specifications around OK channel specifications. (see #586)
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