clean up spaces after comma

Use PetscFunctionBegin instead of PetscFunctionBeginUser

fix a bug related to stack size; allow overwriting top elements in stack

bug fix for checking stack overflow

add in-memory checkpointing, and it works :)

correct more names for TSTrajectory and add TS to the argument list when creating TSTrajectory

fix compile errors

merge nek-style checkpointing here mannually

Merge branch 'hongzh/ts-adjoint-monitor'

refactor the code to prepare for all the three versions of revolve

TSTrajectorySet: replace shell code with PetscRMTree() and PetscMkdir()

fix brackets and names

modify confusing names

change PetscFunctionBeginUser to PetscFunctionBegin

resolve conflict with master 2

resolve conflict with master 1

remove some whitespaces

adjust the scope of revolve macro

revolve configuration works

use macro PETSC_HAVE_REVOLVE

remove revolve sources files from PETSc

skip the starting and ending step correctly

color output messages

Use global stepnum only in the forward sweep, not in the recomputations stage

use global stepnum, and fix error types