Make g_rcutils_log_severity_names public and immutable. (#180)

Signed-off-by: Michel Hidalgo <[email protected]>

Author: hidmic

include/rcutils/logging.h

@@ -172,7 +172,8 @@ enum RCUTILS_LOG_SEVERITY
 };
 
 /// The names of severity levels.
-extern const char * g_rcutils_log_severity_names[RCUTILS_LOG_SEVERITY_FATAL + 1];
+RCUTILS_PUBLIC
+extern const char * const g_rcutils_log_severity_names[RCUTILS_LOG_SEVERITY_FATAL + 1];
 
 /// Get a severity value from its string representation (e.g. DEBUG).
 /**

src/logging.c

@@ -43,7 +43,7 @@ extern "C"
 
 #define RCUTILS_LOGGING_MAX_OUTPUT_FORMAT_LEN (2048)
 
-const char * g_rcutils_log_severity_names[] = {
+const char * const g_rcutils_log_severity_names[] = {
   [RCUTILS_LOG_SEVERITY_UNSET] = "UNSET",
   [RCUTILS_LOG_SEVERITY_DEBUG] = "DEBUG",
   [RCUTILS_LOG_SEVERITY_INFO] = "INFO",