libc: add labs() and llabs()

Add support for abs with additional integer types.

This is needed to make LLVM quiet and stop warning about abs being used
with int64_t and such.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

doc/guides/portability/posix.rst

@@ -261,9 +261,9 @@ This is implemented as part of the minimal C library available in Zephyr.
     isspace(),+
     isupper(),+
     isxdigit(),+
-    labs(),
+    labs(),+
     ldiv(),
-    llabs(),
+    llabs(),+
     lldiv(),
     localeconv(),
     localtime(),+

lib/libc/minimal/include/stdlib.h

@@ -39,7 +39,20 @@ void abort(void);
 
 int rand(void);
 
-#define abs(x) ((x) < 0 ? -(x) : (x))
+static inline int abs(int __n)
+{
+	return (__n < 0) ? -__n : __n;
+}
+
+static inline long labs(long __n)
+{
+	return (__n < 0L) ? -__n : __n;
+}
+
+static inline long long llabs(long long __n)
+{
+	return (__n < 0LL) ? -__n : __n;
+}
 
 #ifdef __cplusplus
 }