PATCH, boehm-gc: silence os_dep.c warnings

[Andrew Haley]

Ben Elliston wrote:
> GNU/Linux systems warn about the BSD signal functions like sigsetmask:
> 
>   warning: ‘sigsetmask’ is deprecated (declared at /usr/include/signal.h:199)
> 
> This patch rearranges some of the code in boehm-gc/os_dep.c so that
> modern systems providing the POSIX signals API are used in preference to
> the BSD API.  This is important on systems like GNU/Linux where both
> APIs are provided.
> 
> As autoconf tests are not used in boehm-gc, I have followed the style of
> tests already used in this file.  Bootstrapping is underway on
> x86_64-linux-gnu.  Okay for the trunk?
> 
> Ben
> 
> 
> 2009-11-27  Ben Elliston  <bje@au.ibm.com>
> 
> 	* os_dep.c: Use the POSIX signal API in preference to the BSD API.
> 	Generate a compilation error if neither the POSIX nor BSD APIs can
> 	be detected.

OK.

Andrew.