A simple, assembly-like syntax for strategies is introduced.
The code for a strategy is now a single string, in the field
'code' of a 'strategy' entry of a configuration file.
See share/strategies.conf for examples.

- move common lexing functions to util/lexlib.mll
- move and rename Typing.create_user_tv to Ty.tv_of_string

two parts: why3 and why3session.

(The Coq tactic does not include why3session)

counts lines/tokens in Why3 files
distinguishes spec (logic declarations and annotations) and code
reports the ratio spec/code with command line option -f

example: why3wc -f examples/*.mlw
see why3wc --help for more details

note: why3wc assumes that input files are lexically well-formed
it also makes some approximations (switching from spec to code and
conversely is only done when there is a blank line in the middle)

support for 31/32/63/64-bit integers in extracted code

Problem: lambda is not extracted into a fun ... -> ...