Class constant for SVN-based plugins min requirement

Following the same logic as for the framework version, we define
SOURCESVN_VERSION_REQUIRED to make it easier to identify and globally
increase the required SourceSVN version in all SVN-based plugins.

Author: dregad

SourceSFSVN/SourceSFSVN.php

@@ -10,6 +10,7 @@
 class SourceSFSVNPlugin extends SourceSVNPlugin {
 
 	const FRAMEWORK_VERSION_REQUIRED = '1.3.2';
+	const SOURCESVN_VERSION_REQUIRED = '0.16';
 
 	public function register() {
 		$this->name = lang_get( 'plugin_SourceSFSVN_title' );
@@ -19,7 +20,7 @@ public function register() {
 		$this->requires = array(
 			'MantisCore' => self::MANTIS_VERSION,
 			'Source' => self::FRAMEWORK_VERSION_REQUIRED,
-			'SourceSVN' => '0.16',
+			'SourceSVN' => self::SOURCESVN_VERSION_REQUIRED,
 		);
 
 		$this->author = 'John Reese';

SourceViewVC/SourceViewVC.php

@@ -11,6 +11,7 @@
 class SourceViewVCPlugin extends SourceSVNPlugin {
 
 	const FRAMEWORK_VERSION_REQUIRED = '1.3.2';
+	const SOURCESVN_VERSION_REQUIRED = '0.16';
 
 	public function register() {
 		$this->name = lang_get( 'plugin_SourceViewVC_title' );
@@ -20,7 +21,7 @@ public function register() {
 		$this->requires = array(
 			'MantisCore' => self::MANTIS_VERSION,
 			'Source' => self::FRAMEWORK_VERSION_REQUIRED,
-			'SourceSVN' => '0.16',
+			'SourceSVN' => self::SOURCESVN_VERSION_REQUIRED,
 		);
 
 		$this->author = 'John Bailey';

SourceWebSVN/SourceWebSVN.php

@@ -10,6 +10,7 @@
 class SourceWebSVNPlugin extends SourceSVNPlugin {
 
 	const FRAMEWORK_VERSION_REQUIRED = '1.3.2';
+	const SOURCESVN_VERSION_REQUIRED = '0.16';
 
 	public function register() {
 		$this->name = lang_get( 'plugin_SourceWebSVN_title' );
@@ -19,7 +20,7 @@ public function register() {
 		$this->requires = array(
 			'MantisCore' => self::MANTIS_VERSION,
 			'Source' => self::FRAMEWORK_VERSION_REQUIRED,
-			'SourceSVN' => '0.16',
+			'SourceSVN' => self::SOURCESVN_VERSION_REQUIRED,
 		);
 
 		$this->author = 'John Reese';