Motivated by the report at  
http://groups.google.com/group/comp.lang.fortran/browse_thread/thread/6373a2dfe64f0b83

There is currently no run-test check that libquadmath actually works. 
The attached and committed (Rev. 181015) adds one which tests for 
libquadmath that I/O read/write works. Additionally, it checks that the 
result for sqrt(2.0) is OK.

The test uses the largest available floating-point number - be it 8, 10 
or 16 - and tests for that. The checks should be thus OK for any system.

Regarding the issue mentioned in the linked report: Kai could reproduce 
the issue - he also gets "0.0" under MinGW64 with the current trunk. 
(The report was for MinGW32 4.7.0 and allegedly it worked for 4.6.2.)

Tobias