refactor: improved line parser

- improved support for C-style comments;
- add support for keys with square brackets;
- slightly improved speed.

test/data/in_ini/test_add_keyval.sh.ini

@@ -1,6 +1,6 @@
 # comment
 ; comment again
-
+	// comment with indent
 DefKey1 = Some Value1
 DefKey2		=	Some Value2 And Tabs! # With Comment
 DefKey3=NoSpaces!

test/data/in_ini/test_get_key_slashes.sh.ini

@@ -0,0 +1,19 @@
+# comment
+; comment again
+
+DefKey1 = Some Value1
+DefKey2		=	Some Value2 And Tabs! # With Comment
+DefKey3=NoSpaces!
+
+[Slashes/Test] // Comment For Section
+	./Dir1/File = skip/skip // comment
+	Key2 = 2
+
+[MultipleKeySection] // C style comment
+	Key = 1
+Key = 2
+	Key = 3
+	
+	[SectionWithIndent]
+	Key=Value
+[SectionWithoutNewLineBefore]