adding macro in petscversion.h

[Lisandro Dalcin]

It it is not too late, I would like to add the following macro in petscversion.h

#if !defined(PETSC_VERSION_)
#define PETSC_VERSION_(MAJOR,MINOR,SUBMINOR)   \
       (PETSC_VERSION_MAJOR    == MAJOR    && \
	PETSC_VERSION_MINOR    == MINOR    && \
	PETSC_VERSION_SUBMINOR == SUBMINOR && \
	PETSC_VERSION_RELEASE  == 1)
#endif

In petsc4py, I have to test the version in many places in order to
provide backward compatibility with previous releases. The new macro
is really handy for this,

#if PETSC_VERSION_(2,3,2)
/* code for the 2.3.2 case */
#elif PETSC_VERSION_(2,3,3)
/* code for the 2.3.2 case */
#elif PETSC_VERSION_(2,4,0)
/* code for latest release (once done)*/
#else
/* code for (future) petsc-dev
#endif

What do you think? Should I remove the last "_" in "PETSC_VERSION_".
Better name?

Of course, it I want to use this for 2.3.2/2.3.3 releases, I would
need to manage that in my code, but from 2.4.0 and above, that would
be already defined for user convenience needing to target the same
code for multiple PETSc releases.


-- 
Lisandro Dalcín
---------------
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
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