Make sure LogPrintf strings are line-terminated

Fix the cases where LogPrint[f] was accidentally called without line
terminator, which resulted in concatenated log lines.

(see e.g. #6492)

src/main.cpp

@@ -3501,7 +3501,7 @@ bool LoadExternalBlockFile(FILE* fileIn, CDiskBlockPos *dbp)
                     }
                 }
             } catch (const std::exception& e) {
-                LogPrintf("%s: Deserialize or I/O error - %s", __func__, e.what());
+                LogPrintf("%s: Deserialize or I/O error - %s\n", __func__, e.what());
             }
         }
     } catch (const std::runtime_error& e) {