Improve XLSX Escaper performance (#305)

tests/Spout/Common/Escaper/XLSXTest.php

@@ -17,7 +17,11 @@ class XLSXTest extends \PHPUnit_Framework_TestCase
         return [
             ['test', 'test'],
             ['adam\'s "car"', 'adam's "car"'],
+            ["\n", "\n"],
+            ["\r", "\r"],
+            ["\t", "\t"],
             [chr(0), '_x0000_'],
+            [chr(4), '_x0004_'],
             ['_x0000_', '_x005F_x0000_'],
             [chr(21), '_x0015_'],
             ['control '.chr(21).' character', 'control _x0015_ character'],
@@ -49,7 +53,11 @@ class XLSXTest extends \PHPUnit_Framework_TestCase
         return [
             ['test', 'test'],
             ['adam's "car"', 'adam\'s "car"'],
+            ["\n", "\n"],
+            ["\r", "\r"],
+            ["\t", "\t"],
             ['_x0000_', chr(0)],
+            ['_x0004_', chr(4)],
             ['_x005F_x0000_', '_x0000_'],
             ['_x0015_', chr(21)],
             ['control _x0015_ character', 'control '.chr(21).' character'],