libc: Expand limits.h and include in stdint.h

Add maximum native integer size and limits of specified-width integer
types.
These types are required by the external library: libpldm.

Signed-off-by: Christophe Lombard <clombard@linux.ibm.com>
Signed-off-by: Reza Arbab <arbab@linux.ibm.com>
diff --git a/libc/include/limits.h b/libc/include/limits.h
index bfde963..0c85d2e 100644
--- a/libc/include/limits.h
+++ b/libc/include/limits.h
@@ -33,5 +33,11 @@
 
 #define 	UINT32_MAX	UINT_MAX
 #define 	INT32_MAX	INT_MAX
+#define		UINT16_MAX	USHRT_MAX
+#define		UINT8_MAX	UCHAR_MAX
+
+#ifndef SIZE_MAX
+#define SIZE_MAX (~0ull)
+#endif
 
 #endif
diff --git a/libc/include/stdint.h b/libc/include/stdint.h
index 2a2c1d9..080d875 100644
--- a/libc/include/stdint.h
+++ b/libc/include/stdint.h
@@ -13,6 +13,9 @@
 #ifndef _STDINT_H
 #define _STDINT_H
 
+/* C99 requires *_MAX to be in stdint.h */
+#include <limits.h>
+
 typedef unsigned char uint8_t;
 typedef signed char int8_t;