[fpc-pascal] BMP support improved, feedback welcome.

[Michael Van Canneyt]

Hi,

Thanks to some excellent work from Giulio Berna, the support for BMP images
in the FCL has been greatly improved (and as such should impact Lazarus)

- BMP Reader enhanced to full Microsoft specs:
  + support for 15,16 bit bitmaps.
  + support for strange color masks at 16, 32 bpp
  + rle4 and rle8 decoding
  + top-down stored bitmaps.
  + Palette behaviour changed: use palette at 1,4,8 bits.
  + Support for OnProgress event.

- BMP Writer support:
  + BitsPerPixel property.
  + Writing at all color depths.
  + RLE8 and RLE4 compression.

I have applied his patches, but am not in the possibility to test all 
these changes. If there are people out there which use a lot of images,
I would welcome some feedback.

More changes (dithering, quantizing) of images have also been implemented
by Giulio, and will be committed soon.

Kudos to Giulio Berna,

Enjoy,

Michael.