If available, use libjpeg-turbo in Debian build dependencies

Debian is transitioning to libjepg-turbo in Jessie.

See the libjpeg-turbo transition plan for details:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=754988

FS-7151 #resolve

debian/bootstrap.sh

@@ -308,7 +308,7 @@ Build-Depends:
  libogg-dev, libspeex-dev, libspeexdsp-dev,
 # configure options
  libssl-dev, unixodbc-dev, libpq-dev,
- libncurses5-dev, libjpeg62-dev | libjpeg8-dev,
+ libncurses5-dev, libjpeg62-turbo-dev | libjpeg62-dev | libjpeg8-dev,
  python-dev, erlang-dev,
 # documentation
  doxygen,