New issue by classabbyamp on void-packages repository

https://github.com/void-linux/void-packages/issues/39976

Description:
[current upstream](https://agg.sourceforge.net/antigrain.com/) only has source for v2.4, we should probably try to move to a different fork and update. debian has [source for the version we package](https://packages.debian.org/stretch/source/agg), but it fails to build:

```
Making all in font_freetype
make[1]: Entering directory '/builddir/agg-2.5+dfsg1/font_freetype'
/bin/sh ../libtool  --tag=CXX   --mode=compile g++ -DHAVE_CONFIG_H -I. -I../include    -I../include -I/usr/include/freetype2 -I/usr/include/libpng16  -fstack-clash-protection -D_FORTIFY_SOURCE=2 -mtune=generic -O2 -pipe    -fdebug-prefix-map=/builddir/agg-2.5+dfsg1=. -MT libaggfontfreetype_la-agg_font_freetype.lo -MD -MP -MF .deps/libaggfontfreetype_la-agg_font_freetype.Tpo -c -o libaggfontfreetype_la-agg_font_freetype.lo `test -f 'agg_font_freetype.cpp' || echo './'`agg_font_freetype.cpp
libtool: compile:  g++ -DHAVE_CONFIG_H -I. -I../include -I../include -I/usr/include/freetype2 -I/usr/include/libpng16 -fstack-clash-protection -D_FORTIFY_SOURCE=2 -mtune=generic -O2 -pipe -fdebug-prefix-map=/builddir/agg-2.5+dfsg1=. -MT libaggfontfreetype_la-agg_font_freetype.lo -MD -MP -MF .deps/libaggfontfreetype_la-agg_font_freetype.Tpo -c agg_font_freetype.cpp  -fPIC -DPIC -o .libs/libaggfontfreetype_la-agg_font_freetype.o
In file included from agg_font_freetype.h:34,
                 from agg_font_freetype.cpp:26:
../include/agg_scanline_u.h: In member function 'void agg::scanline32_u8_am<AlphaMask>::finalize(int)':
../include/agg_scanline_u.h:482:39: error: cannot call member function 'void agg::scanline_u8::finalize(int)' without object
  482 |             base_type::finalize(span_y);
      |                                       ^
../include/agg_scanline_u.h:485:70: error: cannot call member function 'agg::scanline_u8::span* agg::scanline_u8::begin()' without object
  485 |                 typename base_type::iterator span = base_type::begin();
      |                                                                      ^
../include/agg_scanline_u.h:486:55: error: cannot call member function 'unsigned int agg::scanline_u8::num_spans() const' without object
  486 |                 unsigned count = base_type::num_spans();
      |                                                       ^
../include/agg_scanline_u.h:490:62: error: cannot call member function 'int agg::scanline_u8::y() const' without object
  490 |                                                 base_type::y(),
      |                                                              ^
make[1]: *** [Makefile:471: libaggfontfreetype_la-agg_font_freetype.lo] Error 1
make[1]: Leaving directory '/builddir/agg-2.5+dfsg1/font_freetype'
make: *** [Makefile:496: all-recursive] Error 1
```

this is only used by one package (desmume), and it seems that agg is an optional dependency, so maybe it would be better to just remove it.