webservices: Make alloc_float_text() static.

[Hans Leidekker]

On Fri, 2017-09-08 at 02:24 +0200, Francois Gouget wrote:
>  dlls/webservices/reader.c              | 2 +-
>  dlls/webservices/webservices_private.h | 1 -
>  2 files changed, 1 insertion(+), 2 deletions(-)
> 
> It was introduced in 82306e84 on 2017-07-20 and has not been used 
> outside reader.c since then. Ignore this patch if there are ongoing 
> plans to use it elsewhere.

It will be used in the writer at some point.