Add missing RDK_LOG_FATAL constant to fallback definitions

[Copilot]

The RDK_LOG_FATAL constant was referenced in rdkv_cdl_log_wrapper.h:34 but undefined in the fallback definitions when the real RDK logger is unavailable.

Changes:

• Added RDK_LOG_FATAL (value 6) to both fallback constant sets in rdk_debug.h
• Extended the fallback RDK_LOG macro to handle RDK_LOG_FATAL with "FATAL:" prefix
• Added .gitignore for autotools build artifacts

Context:

// rdkv_cdl_log_wrapper.h uses RDK_LOG_FATAL
#define SWLOG_FATAL(format, ...) RDK_LOG(RDK_LOG_FATAL, "LOG.RDK.FWUPG", format"\n", ##__VA_ARGS__)

// Now defined in fallback when rdk_logger.h is unavailable
#define RDK_LOG_FATAL 6  // After RDK_LOG_ERROR (5)

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