Add tests for fegetexceptflag, fesetexceptflag [committed]

[Joseph Myers]

On Wed, 10 Aug 2016, Joseph Myers wrote:

> I noticed that there was no meaningful test coverage for
> fegetexceptflag and fesetexceptflag (one test ensures that calls to
> them compile and link, but nothing to verify they work correctly).

Actually, that existing test (test-fenvinline) verifies some aspects of 
those functions' operation - but not enough, as evidenced by the powerpc 
bug found by my new tests.

Anyway, the thing that made me suspect test coverage was inadequate was 
noticing that sysdeps/alpha/fpu/fsetexcptflg.c appears to clear all 
previously set exceptions unconditionally, regardless of whether specified 
in the mask of flags to be restored that was passed to fesetexceptflag.  
I have not verified this, but would expect the new test test-fexcept to 
fail on Alpha, in which case sysdeps/alpha/fpu/fsetexcptflg.c should be 
fixed accordingly (with bug filed in Bugzilla as usual, etc.).

-- 
Joseph S. Myers
joseph@codesourcery.com