Remove Abs()

All callers have been replaced by standard C library functions.

Reviewed-by: Zhang Mingli <zmlpostgres@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/4beb42b5-216b-bce8-d452-d924d5794c63%40enterprisedb.com

src/include/c.h

@@ -950,12 +950,6 @@ extern void ExceptionalCondition(const char *conditionName,
  */
 #define Min(x, y)		((x) < (y) ? (x) : (y))
 
-/*
- * Abs
- *		Return the absolute value of the argument.
- */
-#define Abs(x)			((x) >= 0 ? (x) : -(x))
-
 
 /* Get a bit mask of the bits set in non-long aligned addresses */
 #define LONG_ALIGN_MASK (sizeof(long) - 1)