tools/mklibs: update to 0.1.44 and convert to Python 3

Since the switch to Python 3 build fails if CONFIG_USE_MKLIBS is set
("Strip unnecessary functions from libraries" in menuconfig) as
mklibs hasn't been converted to run on Python 3.

 * update to most recent upstream version which brings some
   reproducibility fixes
 * converted to Python 3 using 2to3
 * fixed mixed tab/spaces indentation
 * fixed use of string.* functions
 * some more minor fixes to make Python 3 happy

Fixes commit 19938c8de7 ("build: switch to Python 3")
Signed-off-by: Daniel Golle <daniel@makrotopia.org>