CLEANUP: atomic/tree-wide: replace single increments/decrements with inc/dec

This patch replaces roughly all occurrences of an HA_ATOMIC_ADD(&foo, 1)
or HA_ATOMIC_SUB(&foo, 1) with the equivalent HA_ATOMIC_INC(&foo) and
HA_ATOMIC_DEC(&foo) respectively. These are 507 changes over 45 files.
diff --git a/src/ev_kqueue.c b/src/ev_kqueue.c
index bc17480..ee6b8c2 100644
--- a/src/ev_kqueue.c
+++ b/src/ev_kqueue.c
@@ -184,7 +184,7 @@
 		fd = kev[count].ident;
 
 #ifdef DEBUG_FD
-		_HA_ATOMIC_ADD(&fdtab[fd].event_count, 1);
+		_HA_ATOMIC_INC(&fdtab[fd].event_count);
 #endif
 		if (!fdtab[fd].owner) {
 			activity[tid].poll_dead_fd++;