add /utf-8 switch for msvc build. source code has several utf-8 characters
fix C2001 error. escape non-printable ascii code generated by embed_test_data.go
fix C4819 warning. add u8 keyword on utf-8 string literal (ripemd_test.cc)

Change-Id: I8c04dc7f0359e6ee27efada066863826d263d5cd
Reviewed-on: https://boringssl-review.googlesource.com/26484
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>