Resolve Wrestrict warnings on GCC 8.1.1 (#51)

* Fix several misleading indentation warnings on GCC 8.1.1

* Fix reliance on undefined strcpy/sprintf behavior (-Wrestrict warnings)

The standard states that strcpy results in undefined behavior when the source
and destination buffers overlap. I resolved this with a combination of memmove
and strlen. Note that the resulting code is slightly less efficient.

Similarly, sprintf's behavior is undefined when copying takes place between
objects that overlap. I replaced most of these with a simple strcat, though
one required a temp buffer.

* Fix format in improved-edit.c to match surrounding code

src/dg_olc.c

@@ -476,7 +476,8 @@ static void script_syntax_highlighting(struct descriptor_data *d, char *string)
             }
         }
 
-        sprintf(buffer, "%s%s\tn\r\n", buffer, line);
+        strcat(buffer, line);
+        strcat(buffer, "\tn\r\n");
     }
     
     page_string(d, buffer, TRUE);