Use libc_hidden_* for tolower, toupper (bug 15105)

[Florian Weimer]

On 02/22/2018 10:24 PM, Joseph Myers wrote:
> 2018-02-22  Joseph Myers<joseph@codesourcery.com>
> 
> 	[BZ #15105]
> 	* ctype/ctype.c (tolower): Use libc_hidden_def.
> 	(toupper): Likewise.
> 	* include/ctype.h [!_ISOMAC] (tolower): Use libc_hidden_proto.
> 	[!_ISOMAC] (toupper): Likewise.

Looks good.

Thanks,
Florian