[AGG] AGG on Debian and Ubuntu

[John H. <jo...@gl...>]

Debian has a package called libagg-dev that installs libagg.a and all of
the headers for AGG 2.5. This package is orphaned and I am thinking of
taking it over and updating it to AGG 2.4 from SourceForge. Unless we
update AGG 2.4 to 2.6 I will have to create a fictitious Debian version
like 2.5.4.117 to represent AGG 2.4-r117.

I am attaching some patches to AGG 2.4 that come from Debian and Ubuntu:

-- agg24debiancrashfix.diff fixes a crash that happens when drawing really
long lines triggers signed integer overflow in agg_rasterizer_cells_aa.
Debian uses a patch that detects if overflow is likely and doesn't draw the
line. I have replaced it with a patch that uses 64-bit math in a few places
where 32-bit integer math isn't correct.

-- agg24debianfailtobuildfix.diff fixes a build failure on some systems
using clang

-- agg24noUB.diff eliminates another place where signed overflow could
result in undefined behavior. The patch shouldn't effect code generation
but it may inhibit unsafe compiler optimizations.

-- agg24No32bitIntAssumption.diff I noticed that AGG is littered with the
constant 0x7FFFFFFF, INT_MAX for 32-bit integers. This patch replaces all
of them with the INT_MAX/INT_MIN macros.

-- agg24unusedparams.diff This is a patch from my personal copy of AGG. It
just silences some unused parameter warnings.

I have applied all of these patches and then built and run all of the
examples. Everything seemed to be OK.

-- john