Disable checksum calculation

Calculation can take very long. Most Unix-ish OSes have utilities to do this.

README.md

@@ -59,7 +59,7 @@ I chose to fork because:
     - current item in reverse video
     - number of items in current directory
     - full name of currently selected file
-  - Show details of the currently selected file (stat, file, md5, sha256)
+  - Show details of the currently selected file (stat, file)
   - Directories first
   - Sort numeric names in numeric order
   - Case-insensitive alphabetic content listing instead of upper case first

nnn.c

@@ -796,6 +796,8 @@ show_stats(char* fpath, char* fname, struct stat *sb)
 			}
 			printw(" %s", begin);
 		}
+#ifdef SUPPORT_CHKSUM
+		/* Calculating checksums can take VERY long */
 
 		/* Show md5 */
 		sprintf(buf, "openssl md5 \"%s\" 2>&1", fpath);
@@ -822,6 +824,7 @@ show_stats(char* fpath, char* fname, struct stat *sb)
 
 			printw("  sha256: %s", p);
 		}
+#endif
 	}
 
 	/* Show exit keys */