adms-2.3.5 release

adms-2.3.5:

Change license to GPLv3.

Add new simplified constants.vams and discplines.vams.
Tested to work with models currently in use by Qucs, Ngspice, Xyce and Gnucap.
Whenever these headers are used, adms informs the user about the
availability of the standard headers at:
http://accellera.org/downloads/standards/v-ams

Remove non-GPL constants.vams and disciplines.vams headers.
These files are copyright of Accellera. With the LRM v2.4.0 updated versions
of these files are freely accessible. However modification is not allowed.
Hence, these files are not GPL and should not be included in adms.

Autotools, add back support for static and shared libraries build.
Build shared libraries by default. Tested on Linux, Mac OSX, and MSYS2.
See the configure --disable-shared flag to change that.
CMake contiues to builds static libraries only.

Fix out-of-tree build for Autotools and CMake.

Check scaling factors againd LRM v2.4.0
Add missing K scaling (uppercase kilo)
standard scale_factor T|G|M|K|k|m|u|n|p|f|a
Add testset (va and xml files) to test the scaling factors

Handle non-standard scaling factors with warning E|P|D|h|d|c|A
Patch by Geoffrey Coram

Relax Bison requirement, tested with (2.5, 3.0.2)

Perl GD module is no longer required at build time.