Disable the use of memory-mapped I/O if the SQLITE_DISABLE_MMAP macro is

defined.  Automatically define this macro for OpenBSD and QNX.  Other
systems are likely to be added to the disabled list over time.

FossilOrigin-Name: 8a4314a398c6c6efb25e6993c826b7e60d9bb1f9

src/pragma.c

@@ -774,6 +774,9 @@ void sqlite3Pragma(
     }
     mx = -1;
     if( sqlite3_file_control(db,zDb,SQLITE_FCNTL_MMAP_LIMIT,&mx)==SQLITE_OK ){
+#if defined(SQLITE_DISABLE_MMAP)
+      mx = 0;
+#endif
       returnSingleInt(pParse, "mmap_limit", mx);
     }
   }else