Refactor strtod parsing of NaN payloads

[Florian Weimer]

On 11/24/2015 02:55 PM, Joseph Myers wrote:
> On Tue, 24 Nov 2015, Florian Weimer wrote:
> 
>> On 11/21/2015 01:10 AM, Joseph Myers wrote:
>>
>>> 	* include/stdlib.h (__strtof_nan): Declare and use
>>> 	libc_hidden_proto.
>>> 	(__strtod_nan): Likewise.
>>> 	(__strtold_nan): Likewise.
>>> 	(__wcstof_nan): Likewise.
>>> 	(__wcstod_nan): Likewise.
>>> 	(__wcstold_nan): Likewise.
>>
>> This could be marked internal_function, I think (both the declaration
>> and definition).
> 
> The point of this refactoring is so that a future change can call these 
> (libc) functions from the nan* functions in libm.  I don't think 
> internal_function is compatible with PLT calls from other libraries.

internal_function is a bit of a misnomer, it just affects the calling
convention on some architectures.  Unlike attribute_hidden, it does not
interfere with linking, as long as the caller uses the same prototype
(with the internal_function attribute).

Florian