build: formatting, only use #!/usr/bin instead of #! /usr/bin

this is just a cosmetic change.
command to produce this is:
 /usr/bin/vendor_perl/ack -f --python | xargs perl -i -p -e's@#! /usr/bin/env@#!/usr/bin/env@g'
after #! refactor, keep check for both #! and #!<space>

manually fix check for both acceptable cases for shebang
refactoring use python2 : rename all #!/usr/bin/env python

this is first part of refactoring to use python2 instead of python
(python can be python3 now or in near future)

command for this rename:
 /usr/bin/vendor_perl/ack -f --python | xargs perl -i -p -e's@#!/usr/bin/env python@#!/usr/bin/env python2@g'

PS: ack is something like find+grep
manual fix for specific occurence #!<space> python2

this is only 1 occurence in all codebase, all other have been
automatically translated,
refactoring: replace python -> python2 in all shell files

command
/usr/bin/vendor_perl/ack -f --shell | xargs perl -i -p -e's@python @python2 @g'
refactoring: manually fix "python" usage in comment

for previous commit
refactor python2: replace 'python' *.py usage in python files

command used:
/usr/bin/vendor_perl/ack -f --python | xargs perl -i -p -e's@python (.*\.py)@python2 \1@g'
refactor python2: manually fix after prev, commit

in two files:
external/darwin64/lib/python2.6/site-packages/pkg_resources.py
external/linux64/lib/python2.6/site-packages/pkg_resources.py
refactoring python2: replace python->python2 *.py in all other files

command:
/usr/bin/vendor_perl/ack -f | xargs perl -i -p -e's@python (.*\.py )@python2 \1@g'
refactoring python2: final review and manual fix

to review rest 'python ' usage, do:
/usr/bin/vendor_perl/ack -f | xargs grep -e'python ' |grep -v proj|grep -v python2| less
Revert "start porting to python2" - finished!

This file/commit was a placeholder and info, everything seems done now,
so reverting this and head for inclusion. Please test!
This reverts commit c912dd57e3efcb2a2dbaefd6ea910d4b7cdd736c.