[ostream.manip] Rephrase references to exposition-only variable "buf",

and add "Calls" to Effects: clause to match our style guide.

Author: zygoloid

source/iostreams.tex

@@ -6694,7 +6694,8 @@
 \pnum
 \effects
 If \tcode{os.rdbuf()} is a
-\tcode{basic_osyncbuf<charT, traits, Allocator>*} \tcode{buf},
+\tcode{basic_osyncbuf<charT, traits, Allocator>*},
+called \tcode{buf} for the purpose of exposition,
 calls \tcode{buf->set_emit_on_sync(true)}.
 Otherwise this manipulator has no effect.
 \begin{note}
@@ -6719,7 +6720,8 @@
 \pnum
 \effects
 If \tcode{os.rdbuf()} is a
-\tcode{basic_osyncbuf<charT, traits, Allocator>*} \tcode{buf},
+\tcode{basic_osyncbuf<charT, traits, Allocator>*},
+called \tcode{buf} for the purpose of exposition,
 calls \tcode{buf->set_emit_on_sync(false)}.
 Otherwise this manipulator has no effect.
 
@@ -6737,9 +6739,10 @@
 \begin{itemdescr}
 \pnum
 \effects
-\tcode{os.flush()}.
+Calls \tcode{os.flush()}.
 Then, if \tcode{os.rdbuf()} is a
-\tcode{basic_osyncbuf<charT, traits, Allocator>*} \tcode{buf},
+\tcode{basic_osyncbuf<charT, traits, Allocator>*},
+called \tcode{buf} for the purpose of exposition,
 calls \tcode{buf->emit()}.
 
 \pnum