Improve performance of gyp hot functions 

Improve performance of several hot functions identified through 
profiling. 
__init__::DebugOutput 
is_hashable 
FindEnclosingBracketGroup 
IsPathSection 
IsStrCanonicalInt 

Without GYP_PARALLEL these improve gyp_chromium on my Z600 by 
roughly 4s, from 39.5s -> 35.7s. 
With GYP_PARALLEL gains are more modest: ~1s. 

BUG=chromium:82230
Review URL: https://codereview.chromium.org/12330095/

Patch from Isaac Levy <ilevy@chromium.org>!

git-svn-id: http://gyp.googlecode.com/svn/trunk@1583 78cadc50-ecff-11dd-a971-7dbc132099af