Overhaul CrOS post-processing

[jungshik]

• Add touchup_for_cros.py
  • Update version (name table) and revision (OS/2)
  • Drop name table records other than for {pid=3,eid=1,langId=0x409}
• touch_up_web.py
  • apply_web_specific_fixes is split into 2 parts:
    apply_web_cros_common_fixes() and
    apply_web_specific_fixes()
  • Update version (name table) and revision (OS/2)
• temporary_touchups.py
  • Add an optional 'is_for_cros' to apply_tempoary_fixes.
    When is_for_cros is True, usWeightClass is set to 100 for Thin.
    Tthe latest release version of fontconfig on CrOS does not
    distinguish between Thin and Light when it's 250 for Thin.
• Makefile
  • Fix chromeos target

This will fix #179 for CrOS build and #182.

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[jungshik]

@roozbehp and @jamesgk
Can you take a look? I cannot edit the 'assignee' field.

[jungshik]

Let me make a new pull request. When I pushed my branch to github, 'user.email' was set to my chromium.org email address (I haven't registered that email address)