Update to include funcname

When logging with ```SPDLOG_LOGGER_``` macro the ```funcname``` is missing. Updated ```full_formatter``` to include the funcname if source location is present.

include/spdlog/pattern_formatter-inl.h

@@ -978,6 +978,8 @@ public:
             fmt_helper::append_string_view(filename, dest);
             dest.push_back(':');
             fmt_helper::append_int(msg.source.line, dest);
+            dest.push_back(':');
+            fmt_helper::append_string_view(msg.source.funcname, dest);
             dest.push_back(']');
             dest.push_back(' ');
         }