Improve some documentation (#1474)

* Delete removed symbol from PRINTLN examples

* Touch up `SHIFT` docs

Co-authored-by: Sylvie <35663410+Rangi42@users.noreply.github.com>

man/rgbasm.5

@@ -1874,16 +1874,18 @@ then
 will expand to
 .Ql \e<42> .
 .Pp
-Another way to access more than nine macro arguments is the
+The
 .Ic SHIFT
-command, a special command only available in macros.
+directive is only available inside macros.
 It will shift the arguments by one to the left, and decrease
 .Dv _NARG
-by 1.
+by 1:
 .Ic \e1
-will get the value of
+takes the value of
-.Ic \e2 , \e2
+.Ic \e2 ,
-will get the value of
+then
+.Ic \e2
+takes the value of
 .Ic \e3 ,
 and so forth.
 .Pp
@@ -1892,9 +1894,9 @@ can optionally be given an integer parameter, and will apply the above shifting
 A negative parameter will shift the arguments in reverse.
 .Pp
 .Ic SHIFT
-is useful in
+is especially useful in
 .Ic REPT
-blocks to repeat the same commands with multiple arguments.
+loops, to repeat the same commands but with different arguments each time.
 .Ss Printing things during assembly
 The
 .Ic PRINT
@@ -1907,7 +1909,6 @@ PRINT "Hello world!\en"
 PRINTLN "Hello world!"
 PRINT _NARG, " arguments\en"
 PRINTLN "sum: ", 2+3, " product: ", 2*3
-PRINTLN "Line #", __LINE__
 PRINTLN STRFMT("E = %f", 2.718)
 .Ed
 .Bl -inset