Provide the SQLITE_FILE_HEADER command-line option for changing the text

that appears at the beginning of databases. (CVS 2515)

FossilOrigin-Name: 3d7ee5b92d7e30f90cb7a8b3efd649b36480b61b

src/btree.c

@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.261 2005/05/24 20:19:58 drh Exp $
+** $Id: btree.c,v 1.262 2005/06/14 16:04:06 drh Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** For a detailed discussion of BTrees, refer to
@@ -234,8 +234,19 @@ typedef struct MemPage MemPage;
 /*
 ** This is a magic string that appears at the beginning of every
 ** SQLite database in order to identify the file as a real database.
-**                                  123456789 123456 */
-static const char zMagicHeader[] = "SQLite format 3";
+**
+** You can change this value at compile-time by specifying a
+** -DSQLITE_FILE_HEADER="..." on the compiler command-line.  The
+** header must be exactly 16 bytes including the zero-terminator so
+** the string itself should be 15 characters long.  If you change
+** the header, then your custom library will not be able to read 
+** databases generated by the standard tools and the standard tools
+** will not be able to read databases created by your custom library.
+*/
+#ifndef SQLITE_FILE_HEADER /* 123456789 123456 */
+#  define SQLITE_FILE_HEADER "SQLite format 3"
+#endif
+static const char zMagicHeader[] = SQLITE_FILE_HEADER;
 
 /*
 ** Page type flags.  An ORed combination of these flags appear as the