[file.streams] Change sub-clauses to rSec2, similar to [string.streams]

Promote [c.files] to rSec1.

Author: jwakely

source/iostreams.tex

@@ -8456,7 +8456,7 @@
 object converts those multibyte sequences into wide character sequences.
 \exitnote
 
-\rSec3[filebuf]{Class template \tcode{basic_filebuf}}
+\rSec2[filebuf]{Class template \tcode{basic_filebuf}}
 
 \indexlibrary{\idxcode{basic_filebuf}}%
 \begin{codeblock}
@@ -9224,7 +9224,7 @@
 the original contents of the file.
 \end{itemdescr}
 
-\rSec3[ifstream]{Class template \tcode{basic_ifstream}}
+\rSec2[ifstream]{Class template \tcode{basic_ifstream}}
 
 \indexlibrary{\idxcode{basic_ifstream}}%
 \begin{codeblock}
@@ -9464,7 +9464,7 @@
 \tcode{ios_base::failure}~(\ref{iostate.flags})).
 \end{itemdescr}
 
-\rSec3[ofstream]{Class template \tcode{basic_ofstream}}
+\rSec2[ofstream]{Class template \tcode{basic_ofstream}}
 
 \indexlibrary{\idxcode{basic_ofstream}}%
 \begin{codeblock}
@@ -9701,7 +9701,7 @@
 \effects calls \tcode{open(s.c_str(), mode);}
 \end{itemdescr}
 
-\rSec3[fstream]{Class template \tcode{basic_fstream}}
+\rSec2[fstream]{Class template \tcode{basic_fstream}}
 
 \indexlibrary{\idxcode{basic_fstream}}%
 \begin{codeblock}
@@ -9947,7 +9947,7 @@
 \tcode{ios_base::failure}).
 \end{itemdescr}
 
-\rSec2[c.files]{C library files}
+\rSec1[c.files]{C library files}
 
 \pnum
 Table~\ref{tab:iostreams.hdr.cstdio} describes header \tcode{<cstdio>}.