Fix incorrect value in VectorAllocExactLimit
Remove some duplicate/incorrect/useless/weird measurements
Update README
Track maximum height of promise stack
Import R-3.1.0
Merge branch 'vendor' into merge31

Conflicts:
	configure
	src/include/Defn.h
	src/main/context.c
	src/main/duplicate.c
	src/main/eval.c
	src/main/main.c
	src/main/memory.c
Add memory over time measurement
Fix incorrect label in output
Enable mallocmeasure only on Linux
Remove a bit of old, unused code
Do not force KeepSource on
Minor cleanups
function for pseudocontexts, function testing whether contexts are activated
option to print context stack on every begincontext (commented out at the moment)
create context for simple operations (add, multiply) if context scoping is active, too
Revert "debug in gram - needs maintainer-mode to pass into .c file"

Revert done to ease up merging with master. Debugscopes in gram.y are not that important and can be re-inserted if needed, again

This reverts commit 78be9aba74b3e6ff61ed71d735f2ded43ebe895f.
Revert "added debug scope for growData"

Again, this revert was done to get gram.y into a state that merges with master more easily.

This reverts commit 3e215e35ae0e476b911096854f0c3ee097dda3ee.
Merge branch 'master' into debugscopes

Conflicts:
	src/main/context.c
another early return in eval.c prefixed with scope-exit; fixed two merge-errors