Preliminary implementation of a RESCALE_WEIGHTS configuration switch.

Pushed version number to 2.13.1.

Added more complete headers to all files.
Clarified licensing issues.
Updated FITS library.
Updated configuration files.
Added configuration files to the list of data that get installed in ${prefix}/share/sextractor.
Added background offset and point-source model components: FLUX_BACKOFFSET,FLUXERR_BACKOFFSET,FLUX_POINTSOURCE,FLUXERR_POINTSOURCE,MAG_POINTSOURCE,MAGERR_POINTSOURCE.
Tweaked model-fitting convergence parameters.
Fixed catalogue source ordering/number issue in dual-image mode.
Pushed version number to 2.13.0.

Added --disable-model-fitting configure option to turn-off model-fitting features and to allow compiling SExtractor without requiring the ATLAS and FFTW libraries.
Version number pushed to 2.12.0.

Improved real-time display.
Fixed various issues with XSLT in double image mode.
Pushed version number to 2.11.0.

Improved processing time display.

Changed CONCENTRATION_MODEL to SPREAD_MODEL.
Added SPREADERR_MODEL measurement (currently a crude estimate).
Optimized FFT calls.
Set PSF_NMAX to 2 by default.

Removed singular matrix warning.
Added MATRIX_MODELERR measurement parameters.
Added DURATION_ANALYSIS measurement parameter.

Added computation of FLUXERR_MODEL and MAGERR_MODEL.
Fixed a numerical bug in E1MODEL_IMAGE and E2MODEL_IMAGE.
Improved onscreen display.
Pushed version number to 2.8.7