MAT[HERMITIAN]TRANSPOSEVIRTUAL: fix double free with MatMatMult()

Add automatic generated fortran support for setting and returning contexts

Major cleanup of the code for setting and returning application (previously called user) contexts
- PetscCtx ctx is now t

Add automatic generated fortran support for setting and returning contexts

Major cleanup of the code for setting and returning application (previously called user) contexts
- PetscCtx ctx is now the standard for passing in contexts
- PetscCtxRt ctx is the standard for passing out contexts, including context destroy routines based on PetscCtxDestroyFn

Both of these are typedef to void*

Also removed most use of user and userctx for context arguments now consistently named ctx

Improved documentation on PetscCtx and PetscCtxRt and on how to use contexts (including getting them) from Fortran

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MatTranspose: fix MatProduct with non-trivial scaling

Reported-by: Jose E. Roman <jroman@dsic.upv.es>

Change names of Mat_XXX product contexts to MatProductCtx_XXX for code maintainability

Update destroy callback of all MatProductCtx and MatShellSetMatProductOperation() to use PetscCtxDestroyFn

checkbadSource: enforce proper style in makefiles

Change use of void (*)(void) and void (**)(void) in the PETSc API to PetscVoidFn * and PetscVoidFn ** or PetscErrorCodeFn * or PetscErrorCodeFn **