Allow AGG images bigger than 2 GB (#4421)

[rouault]

Necessary changes, but not necessarily sufficient...

[gislars]

Thanks Thomas for pointing me to this patch.
My machine has 12 GB memory so I calculated a image size of 65049x45392 pixel == 11GB.

MapServer version 6.5-dev OUTPUT=PNG OUTPUT=JPEG OUTPUT=KML SUPPORTS=PROJ SUPPORTS=AGG SUPPORTS=FREETYPE SUPPORTS=CAIRO SUPPORTS=SVG_SYMBOLS SUPPORTS=SVGCAIRO SUPPORTS=ICONV SUPPORTS=XMP SUPPORTS=WMS_SERVER SUPPORTS=WFS_SERVER SUPPORTS=WCS_SERVER SUPPORTS=FASTCGI SUPPORTS=GEOS INPUT=JPEG INPUT=POSTGIS INPUT=OGR INPUT=GDAL INPUT=SHAPEFILE

The request is the same, apart from the binary name:

mapserv-test?LAYERS=default&FORMAT=png&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&STYLES=&EXCEPTIONS=application%2Fvnd.ogc.se_inimage&SRS=EPSG%3A900913&BBOX=1402445.0348208,6828711.8836421,1580879.938466,6953224.7330719&WIDTH=65049&HEIGHT=45392&format=agga&map_resolution=1200

The current master with above patch applied is processing the request and is producing a image.
gislars@gisbox:/temp$ file test3.png
test3.png: PNG image data, 65049 x 45392, 8-bit/color RGBA, non-interlaced
gislars@gisbox:/temp$ ll test3.png
-rw-rw-r-- 1 gislars gislars 151895085 Jan 28 15:47 test3.png

The current master without above patch applied is crashing with the following log:
[Tue Jan 28 15:40:43 2014] [error] agg2CreateImage(): Memory allocation error. /root/tools/mapserver/mapagg.cpp: 814: Out of memory allocating 3220882240 bytes.
[Tue Jan 28 15:40:43 2014] [error]
[Tue Jan 28 15:40:43 2014] [error] msDrawMap(): Image handling error. Unable to initialize image.
[Tue Jan 28 15:40:43 2014] [error] agg2CreateImage(): Memory allocation error. /root/tools/mapserver/mapagg.cpp: 814: Out of memory allocating 3220882240 bytes.
[Tue Jan 28 15:40:43 2014] [error]
[Tue Jan 28 15:40:43 2014] [error] msImageCreate(): Memory allocation error. Unable to create new image object.
[Tue Jan 28 15:40:43 2014] [error] Premature end of script headers: mapserv-test

[tbonfort]

applied in 344e7de