Consistently using __throw_*

[Paolo Carlini]

Jonathan Wakely wrote:

>>	__throw (which boils down to either throw or abort)
>>    
>>
>If that is to be used in place of "throw;" then isn't that what
>__throw_exception_again() is intended for?  It doesn't abort() but does
>it need to?  Is it not enough to just let a "throw;" statement compile
>with -fno-exceptions ?
>
>If -fno-exceptions was given then we will already have aborted when the
>original __throw_xxx function was run, unless the exception we've caught
>was thrown by user code.
>  
>
Indeed, I mean to add a __throw exactly for throws from "user code", that is
testcases (see, in particular, many cases in 27_io/basic_istream and 
ostream).
There are also a few instances in testsuite_abi.cc and testsuite_hooks.cc.

Ideally, we should be able to build and regtest cleanly with 
-fno-exceptions...

Paolo.