python: Enforce absolute imports for Python 3 compatibility

Change-Id: Ia88d7fd472f7aed9b97df81468211384981bf6c6
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/15983
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

python: Make iterator handling Python 3 compatible

Many functions that used to return lists (e.g., dict.items()) now
return iterators and their iterator counterparts (e.g.,
dict.iteritems()) have been removed. Switch calls to the Python 2.7
iterator methods to use the Python 3 equivalent and add explicit list
conversions where necessary.

Change-Id: I0c18114955af8f4932d81fb689a0adb939dafaba
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/15992
Reviewed-by: Juha Jäykkä <juha.jaykka@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

python: Replace deprecated repr syntax

Change-Id: I5f9538cf2ca5ee17c51e7c5388d3aef363fcfa54
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/15989
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>

scons: Switch from the print statement to the print function.

Starting with version 3, scons imposes using the print function instead
of the print statement in code it processes. To get things building
again, this change moves all python code within gem5 to use the
function version. Another change by another author separately made this
same change to the site_tools and site_init.py files.

Change-Id: I2de7dc3b1be756baad6f60574c47c8b7e80ea3b0
Reviewed-on: https://gem5-review.googlesource.com/8761
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>

SortedDict: add functions for getting ranges of keys, values, items

python: add a sorted dictionary class
It would be nice if python had a tree class that would do this for real,
but since we don't, we'll just keep a sorted list of keys and update
it on demand.