test for vsnprintf in BuildSystem

[Satish Balay]

Cygwin also provides this function - but not a prototype..

I think I tried to do the code this way so that things work with both
old and new version of visual studio..

Have to figureout a way around this [warning is ok for gcc, but g++
will break on compile..]

Satish

On Tue, 31 Mar 2009, Lisandro Dalcin wrote:

> Satish, do you remember why?:
> 
> $ hg log -r 2219
> changeset:   2219:b2d7f7d19b64
> parent:      2217:08f36f5dec9b
> user:        balay at mcs.anl.gov
> date:        Fri Jan 30 17:53:26 2009 -0600
> summary:     WIndows fix. If '_vsnprintf' exists - then don't check
> for HAVE_VSNPRINTF_CHAR
> 
> I'm getting this warning when building on Cygwin (with GCC):
> 
> libfast in: /cygdrive/c/DEVEL/petsc-dev-cygwin/src/sys/fileio
> mprint.c: In function 'PetscVSNPrintf':
> mprint.c:106: warning: implicit declaration of function '_vsnprintf'
> 
> 
>