Squiz/ComparisonOperatorUsage: handle FQN true/false/null

This commit fixes the sniff to handle "fully qualified true/false" the same as unqualified true/false after the merge of #1020.

Includes tests.

Author: jrfnl

src/Standards/Squiz/Sniffs/Operators/ComparisonOperatorUsageSniff.php

@@ -174,6 +174,13 @@ public function process(File $phpcsFile, $stackPtr)
                 $foundBooleans++;
             }
 
+            if ($tokens[$i]['code'] === T_NAME_FULLY_QUALIFIED) {
+                $compareReadyKeyword = strtolower($tokens[$i]['content']);
+                if ($compareReadyKeyword === '\true' || $compareReadyKeyword === '\false') {
+                    $foundBooleans++;
+                }
+            }
+
             if ($tokens[$i]['code'] === T_BOOLEAN_AND
                 || $tokens[$i]['code'] === T_BOOLEAN_OR
             ) {

src/Standards/Squiz/Tests/Operators/ComparisonOperatorUsageUnitTest.inc

@@ -146,3 +146,9 @@ if (unqualified($argTags > 0)) {}
 if (Partially\qualified($argTags > 0)) {}
 if (\Fully\qualified($argTags > 0)) {}
 if (namespace\relative($argTags > 0)) {}
+
+// Verify that FQN true/false are handled the same as unqualified.
+if (true) {}
+if (\true) {}
+for ($var1 = 10; FALSE; $var1--) {}
+for ($var1 = 10; \FALSE; $var1--) {}