Refactor the logger

[swift-kim]

• Switch to C++-style streams from printf-like (C-style) function macros.
  • Inspired by the FML logger.
  • Introduce two new classes: Logger, LogMessage.
  • Avoid log level abbreviation, e.g. FT_LOGE → FT_LOG(Error).
• Clean up unused debug macros (FT_RELEASE_ASSERT, FT_COMPILE_ASSERT).
  • Instead, a new log level (Fatal) has been added which terminates the process immediately.
• Remove some redundant logs.
• Reword or simplify log messages for clarity and consistency.
• Merge tizen_log.cc and tizen_log_stub.cc into one file.
• Rename tizen_log.h to logger.h.
• Do not print detailed EGL error messages, instead, use stringification to print enum names only.
• Re-enable the --verbose-system-logs option by fixing typo in the arg name (verbose-logging → --verbose-logging).

Sorry for another large commit. The change couldn't be divided into smaller commits.

[bwikbs]

I like old style(printf-like) better.. but It looks like much more trendy code! 😄

[swift-kim]

@bwikbs I also find the printf-style logs are more readable and easy to format in some cases, but the stream style has some benefits as explained in the Google style guide.

The << and >> stream operators provide an API for formatted I/O that is easily learned, portable, reusable, and extensible. printf, by contrast, doesn't even support std::string, to say nothing of user-defined types, and is very difficult to use portably. printf also obliges you to choose among the numerous slightly different versions of that function, and navigate the dozens of conversion specifiers.

I guess the portability here means the need to use format specifiers like %zu and macros like PRId64 for compatibility between 32-bit and 64-bit machines.

[bwikbs]

@swift-kim 👍 I can't say a word..

[swift-kim]

@bbrto21 I changed the log level of some messages in text_input_channel.cc from Info to Debug during the rebase, because there were too many logs printed out to the console. Are you okay with it?