Log Message:
Mechanically replace references to graphics/jpeg with the suitable
alternative from mk/jpeg.buildlink3.mk

This allows selection of an alternative jpeg library (namely the x86 MMX,
SSE, SSE2 accelerated libjpeg-turbo) via JPEG_DEFAULT=libjpeg-turbo, and
follows the current standard model for alternatives (fam, motif, fuse etc).

The mechanical edits were applied via the following script:

#!/bin/sh
for d in *; do
  [ -d "$d" ] || continue
  for i in "$d/"Makefile* "$d/"*.mk; do
    case "$i" in *.orig|*"*"*) continue;; esac
    out="$d/x"
    sed -e 's;graphics/jpeg/buildlink3\.mk;mk/jpeg.buildlink3.mk;g' \
        -e 's;BUILDLINK_PREFIX\.jpeg;JPEGBASE;g' \
        < "$i" > "$out"
    if cmp -s "$i" "$out"; then
      rm -f "$out"
    else
      echo "Edited $i"
      mv -f "$i" "$i.orig" && mv "$out" \ 
"$i"
    fi
  done
done