bugfix-2.0.x critical fix (#7401)

* Fix mistake in gitignore file and add in missing core files.

The missing leading slash on "lib" meant all folders names lib in the directory tree are ignored, rather than just the top level PlatformIO lib folder

* Add LiquidCrystal Library and associated headers modified to compile.

Marlin/frameworks/CMSIS/LPC1768/lib/chanfs/rtc176x.h

@@ -0,0 +1,22 @@
+#ifndef _RTC_DEFINED
+#define _RTC_DEFINE
+
+#include "integer.h"
+#include "LPC176x.h"
+
+typedef struct {
+	WORD	year;	/* 1..4095 */
+	BYTE	month;	/* 1..12 */
+	BYTE	mday;	/* 1.. 31 */
+	BYTE	wday;	/* 1..7 */
+	BYTE	hour;	/* 0..23 */
+	BYTE	min;	/* 0..59 */
+	BYTE	sec;	/* 0..59 */
+} RTC;
+
+int rtc_initialize (void);		/* Initialize RTC */
+int rtc_gettime (RTC*);			/* Get time */
+int rtc_settime (const RTC*);	/* Set time */
+DWORD get_fattime (void);
+
+#endif