C/C++: Improvemed comment pattern (#2229)

This improves the `comment` pattern by allowing backslash-escaped line breaks in single-line comments.

components/prism-c.js

@@ -1,4 +1,8 @@
 Prism.languages.c = Prism.languages.extend('clike', {
+	'comment': {
+		pattern: /\/\/(?:[^\r\n\\]|\\(?:\r\n?|\n|(?![\r\n])))*|\/\*[\s\S]*?(?:\*\/|$)/,
+		greedy: true
+	},
 	'class-name': {
 		pattern: /(\b(?:enum|struct)\s+(?:__attribute__\s*\(\([\s\S]*?\)\)\s*)?)\w+/,
 		lookbehind: true

tests/languages/c/comment_feature.test

@@ -0,0 +1,26 @@
+//
+// comment
+// the comment \
+   continues!
+
+/**/
+/*
+ * comment
+ */
+
+/* open-ended comment
+
+----------------------------------------------------
+
+[
+	["comment", "//"],
+	["comment", "// comment"],
+	["comment", "// the comment \\\r\n   continues!"],
+	["comment", "/**/"],
+	["comment", "/*\r\n * comment\r\n */"],
+	["comment", "/* open-ended comment"]
+]
+
+----------------------------------------------------
+
+Checks for comments.

tests/languages/cpp/comment_feature.test

@@ -0,0 +1,26 @@
+//
+// comment
+// the comment \
+   continues!
+
+/**/
+/*
+ * comment
+ */
+
+/* open-ended comment
+
+----------------------------------------------------
+
+[
+	["comment", "//"],
+	["comment", "// comment"],
+	["comment", "// the comment \\\r\n   continues!"],
+	["comment", "/**/"],
+	["comment", "/*\r\n * comment\r\n */"],
+	["comment", "/* open-ended comment"]
+]
+
+----------------------------------------------------
+
+Checks for comments.

tests/languages/objectivec/comment_feature.test

@@ -0,0 +1,26 @@
+//
+// comment
+// the comment \
+   continues!
+
+/**/
+/*
+ * comment
+ */
+
+/* open-ended comment
+
+----------------------------------------------------
+
+[
+	["comment", "//"],
+	["comment", "// comment"],
+	["comment", "// the comment \\\r\n   continues!"],
+	["comment", "/**/"],
+	["comment", "/*\r\n * comment\r\n */"],
+	["comment", "/* open-ended comment"]
+]
+
+----------------------------------------------------
+
+Checks for comments.