Deprecate uppercase severity names

Jenkinsfile

@@ -63,6 +63,7 @@ pipeline{
             [os: 'fedora', ver: '33',    arch: 'x86_64', compiler: 'gcc-10'],
             [os: 'fedora', ver: '34',    arch: 'x86_64', compiler: 'gcc-11'],
             [os: 'macos',  ver: '11',    arch: 'x86_64', compiler: 'apple-clang-12'],
+            [os: 'macos',  ver: '11',    arch: 'arm64',  compiler: 'apple-clang-13'],
           ])
 
           parallel(builds)

logger/Logger.h

@@ -26,6 +26,7 @@
 
 #include <fmt/core.h>
 #include <fmt/printf.h>
+#include <fmt/ostream.h>
 
 #pragma GCC diagnostic pop
 
@@ -68,19 +69,19 @@ enum class Severity : int
     // aliases
     warning = warn,
     // backwards-compatibility
-    NOLOG = nolog,
+    NOLOG __attribute__((deprecated("Use LOG(nolog) instead (lowercase severity name)."))) = nolog,
-    TRACE = trace,
+    FATAL __attribute__((deprecated("Use LOG(fatal) instead (lowercase severity name)."))) = fatal,
-    DEBUG4 = debug4,
+    ERROR __attribute__((deprecated("Use LOG(error) instead (lowercase severity name)."))) = error,
-    DEBUG3 = debug3,
+    WARN __attribute__((deprecated("Use LOG(warn) instead (lowercase severity name)."))) = warn,
-    DEBUG2 = debug2,
+    WARNING __attribute__((deprecated("Use LOG(warning) instead (lowercase severity name)."))) = warn,
-    DEBUG1 = debug1,
+    STATE __attribute__((deprecated("Use LOG(state) instead (lowercase severity name)."))) = state,
-    DEBUG = debug,
+    INFO __attribute__((deprecated("Use LOG(info) instead (lowercase severity name)."))) = info,
-    INFO = info,
+    DEBUG __attribute__((deprecated("Use LOG(debug) instead (lowercase severity name)."))) = debug,
-    STATE = state,
+    DEBUG1 __attribute__((deprecated("Use LOG(debug1) instead (lowercase severity name)."))) = debug1,
-    WARNING = warn,
+    DEBUG2 __attribute__((deprecated("Use LOG(debug2) instead (lowercase severity name)."))) = debug2,
-    WARN = warn,
+    DEBUG3 __attribute__((deprecated("Use LOG(debug3) instead (lowercase severity name)."))) = debug3,
-    ERROR = error,
+    DEBUG4 __attribute__((deprecated("Use LOG(debug4) instead (lowercase severity name)."))) = debug4,
-    FATAL = fatal
+    TRACE __attribute__((deprecated("Use LOG(trace) instead (lowercase severity name)."))) = trace
 };
 
 // verbosity levels: