Remove writing useless abbreviation by the PNaCl bitcode writer.

That is: TYPE_POINTER_ABBREV  [8, fixed(3), 0]

BUG=None
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/294213003

(cherry picked from commit 3716ccf5969430e9c6a4b033f7fa1af2c4ce4b30)

Conflicts:
	test/NaCl/Bitcode/pnacl-bcdis/global-with-neg-offset.ll
	test/NaCl/Bitcode/pnacl-bcdis/globals-ending-with-compound.ll
	test/NaCl/Bitcode/pnacl-bcdis/globals.ll
	test/NaCl/Bitcode/pnacl-bcdis/no-abbreviations.ll
	test/NaCl/Bitcode/pnacl-bcdis/types-and-fcn-addrs.ll