This include dir is used when using not-installed plumed.
Before this fix, using
./configure --prefix=$PWD
was leading to problems related to the overlap between
installed include files and this directory.
After this fix, it will be possible to configure plumed with
./configure --prefix=$PWD

Updated headers for VES

Thanks @hanatok!

Updated lepton to work with the following versions of asmjit:

b7f6d1e369b4b87006851ded9017d3f864ee9d4b
Thu Jan 26 15:55:03 2017
to
673dcefaa048c5f5a2bf8b85daf8f7b9978d018a
Mon Dec 11 02:02:44 2017

Use an example from a more recent asmjit version

Updated lepton in order to work with the following versions on asmjit:
3fcd65cf805dcd4bbd5fe89a11993dabd01d7b3d
Mon Dec 7 07:34:25 2015
to
fb9f82cb61df36aa513d054e748dc6769045f33e
Fri Nov 11 22:34:49 2016

NOTICE THAT AS OF NOW THE LEPTON LIBRARY INCLUDED IN PLUMED WILL BE
MODIFIED WRT THE ONE INCLUDED IN OPENMM

Reimported lepton fixing the include and ASMJIT guards.

Notice that an old version (compatible with lepton) is currently required.
See the next commits for a newer asmjit version.

Some test for the leptonx2 optimization.
Also some test for different functions.

It is not possible to use x2 as a variable. In this case,
sqrt of distance won't be computed.

Actions are now shown in order also when they are more than 10.
Perhaps should be cleaned up a bit, but it works.

Also this after a discussion with @marcodelapierre

thanks to @marcodelapierre