Make bitcode wrapper info available to MetadataExtractor.

Copy bitcode wrapper information (compiler version, optimization
level) from bitcode wrapper to Module metadata, where it can be found
by MetadataExtractor instantiated from Module.  Previously, such a
MetadataExtractor ignored the information in the bitcode wrapper;
instead, it
- nonsensically set compiler version to RS_VERSION, which is an API
  level rather than a slang version; and
- set optimization level to 3.

Remove unused MetadataExtractor::getTargetAPI():
- Old behavior:
  - For user bitcode, got actual targetAPI.
  - For libclcore, got 0.
  - For linked bitcode (user bitcode + libclcore), got
    uninitialized/garbage value.
- It's not clear what a sensible value would be for libclcore or for
  linked bitcode (or perhaps it should be an error to query the
  targetAPI in those cases).  What a sensible value would be depends
  on how we intend to use it.

This change enables a forthcoming libbcc change that needs to know the
slang version.

Bug: http://b/29154200
Bug: http://b/28070272

Test: full_fugu-eng
      Tried (  modified slang, modified bcc) and
            (unmodified slang, modified bcc):
      - libbcc/tests/run_lit_tests.sh; RsTest; cts -m RenderscriptTest
      - confirmed that our driver is loaded rather than libPVRRS.so
      - By instrumenting modified bcc and running RsTest, confirmed
that:
        - MetadataExtractor properly obtains slang version from Module.
      "Modified slang" is a forthcoming slang change that changes
        the slang version.

Change-Id: Ifc9c1348c96a88bf7ddb344721f67f89359a4fe6
11 files changed