DMPlex: Now a label can be used to restrict the points for a cohesive submesh
- Added label and value arguments to DMPlexCreateCohesiveSubmesh()
PCBDDC: Constraints setup improved

 - Change of basis is now performed using QR factorization of constraints
 - Added missing support for complexes when PETSC_MISSING_GESVD is defined
 - Improved code readability
PCBDDC: Less tricky loop on constraints when changing the basis
PCBDDC: protect queries to lapack GESVD/SYEV when there are no edges or faces (1D)
PCBDDC: Remove aliased parameters from SYEV calls.

Improved readibility
PCBDDC: Remove aliased parameters from GESVD calls
PCBDDC: Remove aliased parameters from GEMM calls.

Improved readibility
PCBDDC: Remove aliased parameter from DDOT call
PCBDDC: Remove aliased parameters for QR calls

Improved readibility
PCBDDC: further improvements to BLAS/LAPACK calls readibility

min_n replaced by k to fullfill code developing guidelines
DMPlex: Fixes for cohesive label reconstruction
- Do not put cohesive edges in labels
- Do not reconstruct "depth" label
DMPlex: Fix hybrid bounds for interpolated mesh with cohesive cells
add an impl of MatGetRedundantMatrix_MPIAIJ_psubcomm() using MatGetSubMatrices()
new impl of MatGetRedundantMatrix_MPIAIJ() works, but needs cleanup
PCGAMG: Always rebuild coarse Mat the first time

The old conditional assumed that, if (!pc_gamg->repart), then the only coarse
matrix that needs to be rebuilt from scratch is on level 0.  If the user has
changed pc_gamg->min_eq_proc, matrices higher in the hierarchy may also need to
be rebuilt from scratch.
Merge branch 'toby/pcgamg-rebuild-coarse' into next

* toby/pcgamg-rebuild-coarse:
  PCGAMG: Always rebuild coarse Mat the first time

Destination: maint (bug fix when changing min_eq_proc)
hdf5: fix so that -Lpath is also used in hdf5 lib check. [fixes --download-hdf5]
Merge branch 'barry/fix-hdf5' into next
Removed extraneous SNESSetInitialFunctionNorm().

The norm is cached on vec_func after copy, so this is unnecessary.
Merge branch 'prbrune/snes-removesetfunctionnorm' into next

Conflicts:
	src/snes/impls/composite/snescomposite.c