Make ENDL optional like ENDSECTION (#1538)

Add warning for `LOAD` without `ENDL`

man/rgbasm.5

@@ -903,7 +903,7 @@ SECTION "LOAD example", ROMX
 CopyCode:
     ld de, RAMCode
     ld hl, RAMLocation
-    ld c, RAMLocation.end - RAMLocation
+    ld c, RAMCode.end - RAMCode
 \&.loop
     ld a, [de]
     inc de
@@ -927,8 +927,8 @@ RAMLocation:
 
 \&.string
     db "Hello World!\e0"
-\&.end
   ENDL
+\&.end
 .Ed
 .Pp
 A
@@ -938,7 +938,9 @@ block feels similar to a
 declaration because it creates a new one.
 All data and code generated within such a block is placed in the current section like usual, but all labels are created as if they were placed in this newly-created section.
 .Pp
-In the example above, all of the code and data will end up in the "LOAD example" section.
+In the example above, all of the code and data will end up in the
+.Dq LOAD example
+section.
 You will notice the
 .Sq RAMCode
 and
@@ -950,6 +952,19 @@ You cannot nest
 .Ic LOAD
 blocks, nor can you change or stop the current section within them.
 .Pp
+The current
+.Ic LOAD
+block can be ended by using
+.Ic ENDL .
+This directive is only necessary if you want to resume writing code in its containing ROM section.
+Any of
+.Ic LOAD , SECTION , ENDSECTION ,
+or
+.Ic POPS
+will end the current
+.Ic LOAD
+block before performing its own function.
+.Pp
 .Ic LOAD
 blocks can use the
 .Ic UNION