postmortem: export kSmiShiftSize

Right now it's impossible to figure out from headers that smis are left shifted
by 31 bit on x64, and only then tagged.

R=erik.corry@gmail.com

Review URL: https://codereview.chromium.org/11676005
Patch from Fedor Indutny <fedor@indutny.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13285 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

tools/gen-postmortem-metadata.py

@@ -76,6 +76,7 @@ consts_misc = [
     { 'name': 'SmiTag',                 'value': 'kSmiTag' },
     { 'name': 'SmiTagMask',             'value': 'kSmiTagMask' },
     { 'name': 'SmiValueShift',          'value': 'kSmiTagSize' },
+    { 'name': 'SmiShiftSize',           'value': 'kSmiShiftSize' },
     { 'name': 'PointerSizeLog2',        'value': 'kPointerSizeLog2' },
 
     { 'name': 'prop_idx_transitions',