It's bison 2.5 that's actually required now.
build system: replace hard-coded flex include dir with that found by autoconf, #575
doc: dates subtraction has two functionalities
doc: fix example
dseries: fix display when TABLE is empty
Allows to use alternative algorithms to solve lyapunov equation
Speeds up the Kalman smoother
Merge pull request #577 from FerhatMihoubi/master

2 additional commits
Release notes for 4.4.1
Fix octave versions.
Fixed bug (a string passed to a dseries object can be a date).
Fixed bug. Allow selection of an observation with a date defined in a formatted string.
Implement broadcasting for operations (+,-,* and /) between dseries and scalar or vectors. Efficiency and cosmetic changes.
Allow assignation of variables in an empty dseries object.
Fixed typo in manual.
Update manual according to commit 117f338effd2dd64021666a3f1bc610058c0b7e8.
Finalize release notes for 4.4.1.
Fixed example ep/rbcii.mod (RBC model with endogenous labour supply and irreversible investment).

The leaded lagrange multiplier (associated with the positivity constraint on investment) was missing in the Euler equation.
Minor fix to release announcement.
doc fix typo