Include fmt/ostream.h, needed for on the fly std::ostream usage

This reverts commit ba7da2f79a.

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   [[deprecated("Use 'nolog' instead")]]   = nolog,
+    NOLOG = nolog,
-    TRACE   [[deprecated("Use 'trace' instead")]]   = trace,
+    TRACE = trace,
-    DEBUG4  [[deprecated("Use 'debug4' instead")]]  = debug4,
+    DEBUG4 = debug4,
-    DEBUG3  [[deprecated("Use 'debug3' instead")]]  = debug3,
+    DEBUG3 = debug3,
-    DEBUG2  [[deprecated("Use 'debug2' instead")]]  = debug2,
+    DEBUG2 = debug2,
-    DEBUG1  [[deprecated("Use 'debug1' instead")]]  = debug1,
+    DEBUG1 = debug1,
-    DEBUG   [[deprecated("Use 'debug' instead")]]   = debug,
+    DEBUG = debug,
-    INFO    [[deprecated("Use 'info' instead")]]    = info,
+    INFO = info,
-    STATE   [[deprecated("Use 'state' instead")]]   = state,
+    STATE = state,
-    WARNING [[deprecated("Use 'warning' instead")]] = warn,
+    WARNING = warn,
-    WARN    [[deprecated("Use 'warn' instead")]]    = warn,
+    WARN = warn,
-    ERROR   [[deprecated("Use 'error' instead")]]   = error,
+    ERROR = error,
-    FATAL   [[deprecated("Use 'fatal' instead")]]   = fatal
+    FATAL = fatal
 };
 
 // verbosity levels: