- printf that looks like debug/status info or disabled by macro/comments
mostly turned to corresponding nyx_debug()
- printf followed by exit/abort/assert turned to nyx_error(),
or nyx_abort() if the error is unlikely to need backtrace/gdb
- non-fatal error/warning messages turned to nyx_warn()
- few hardcoded printf remain, e.g. hexdump and debug helpers
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