Use -march=native for platform-specific optimizations
Use predefined macros to enable SSE with gmake
Add perf tests for EncodedInputStream and AutoUTFInputStream
Fix MemoryStream::Peek() and add test for fix

MemoryStream::Peek() did not return '\0' if src_ == end_, but Peek() == '\0' is
used in parsing in the GenericReader. Without this change, parsing with
MemoryStream as the InputStream could result in a segmentation fault.
Merge pull request #164 from spl/gmake-sse

Use predefined macros to enable SSE with gmake
Merge pull request #165 from spl/perf-test-encoded-and-autoutf-input-streams

Add perf tests for EncodedInputStream and AutoUTFInputStream
Merge pull request #163 from spl/march-native

Use -march=native for platform-specific optimizations
Merge pull request #166 from spl/fix-memorystream-peek

Fix MemoryStream::Peek() and add test for fix