Add php_pdo_sqlite_external.dll to windows build.

This allows the user to provide their own version of sqlite3.dll.
The php_pdo_sqlite.dll is still there, and will continue to be there.
It is built from the bundled sources.
[[DOC]]
 (this should cc: phpdoc, if it's wrong, please let the docs folks know :-)

Author: wez

NEWS

@@ -23,6 +23,9 @@ PHP                                                                        NEWS
 - Added tidyNode::getParent() method (John, Nuno)
 - Added openbasedir and safemode checks in zip:// stream wrapper and 
   ZipArchive::open (Pierre)
+- Added php_pdo_sqlite_external.dll, a version of the PDO SQLite driver that
+  links against an external sqlite3.dll.  This provides Windows users to upgrade
+  their sqlite3 version outside of the PHP release cycle.  (Wez, Edin)
 - Fixed shmop_open() with IPC_CREAT|IPC_EXCL flags on Windows. 
   (Vladimir Kamaev, Tony).
 - Fixed possible leak in ZipArchive::extractTo when safemode checks fails (Ilia)

ext/pdo_sqlite/config.w32

@@ -29,3 +29,10 @@ if (PHP_PDO_SQLITE != "no") {
 	ADD_EXTENSION_DEP('pdo_sqlite', 'pdo');
 }
 
+ARG_WITH("pdo-sqlite-external", "for pdo_sqlite support from an external dll", "no");
+if (PHP_PDO_SQLITE_EXTERNAL != "no") {
+	CHECK_HEADER_ADD_INCLUDE("sqlite3.h", "CFLAGS_PDO_SQLITE_EXTERNAL", PHP_PDO_SQLITE_EXTERNAL + ";" + PHP_PHP_BUILD + "\\include\\sqlite3");
+	CHECK_LIB("sqlite3-import.lib", "pdo_sqlite_external", PHP_PDO_SQLITE_EXTERNAL + ";" + PHP_PHP_BUILD + "\\lib");
+	EXTENSION("pdo_sqlite_external", "pdo_sqlite.c sqlite_driver.c sqlite_statement.c", null, "/I" + configure_module_dirname, null, "ext\\pdo_sqlite_external");
+	ADD_EXTENSION_DEP('pdo_sqlite_external', 'pdo');
+}