build: allow verbose build in nodist

Use "make" or "make V=0" to get the usual silent build but allow
"make V=1" for verbose build. This is required while debugging.
doc: new algorithm for offseting Bézier cubics

Description of the algorithm that will likely substitute the current
offset code.
doc: rename offset to baioca

I'm planning to put another offset algorithm description here (taken
from the actual code), so I need to use two different file names:
"offset" is too generic.
doc: move old algorithm description on its own

Removed description of the offset algorithm for cubic Bézier curve from
the source code to its own PDF inside nodist/ directory.

Renamed two letters variables to an arbitrary one-letter so it can be
expressed better in mathematical formulae.
cpml: add support for custom offset algorithm

In preparation to the inclusion of BAIOCA, added support to the CPML
library for additional offsetting algorithm on cubic Bézier curves.
Added a stub function for hosting the BAIOCA algorithm and implemented
the relevant GUI modification to cpml-demo.
cpml: add cpml_curve_put_offset_at_time() helper method

Offsetting a point at a specific time is heavily used by the Bézier
offseting algorithms, either handcraft and baioca.
doc: correct BAIOCA scalar products

The products between vectors are scalar products: highlighted in the doc
and removed vector notation on the results. Reformatted to make the
lines fit the page width.
cpml-demo: use cpml_curve_put_offset_at_time() for rays

In addition to simplify the code, this will also allow visual debugging
of that function.
doc: improve t_i methods section in BAIOCA

Corrected formatting, renamed variables to avoid clashes and corrected
some documentation bug in the section "Choosing t_i".
doc: cosmetic improvements on baioca.tex

Using more idiomatic tags for math.
doc: correct and simplify baioca algorithm

There was a sign error somewhere: I changed and simplified the formulae
anyway and the error went away.
doc: remove duplication formula in baioca

Further simplification by removing some redundant math: the equation for
calculating Q_0 and Q_3 was bogus because Q_0 = C_0 and Q_3 = C_n.
cpml: add BAIOCA offset implementation

Implemented BAIOCA as described in nodist/baioca.tex. The result is
still suboptimal, hence BAIOCA is not the default offsetting algorithm.