sigaction.2, makecontext.3: Change getcontext/setcontext page ref to Section 3

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man2/sigaction.2

@@ -147,7 +147,7 @@ as its second argument and a pointer to a
 (cast to \fIvoid\ *\fP) as its third argument.
 (Commonly, the handler function doesn't make any use of the third argument.
 See
-.BR getcontext (2)
+.BR getcontext (3)
 for further information about
 .IR ucontext_t .)
 .PP

man3/makecontext.3

@@ -36,8 +36,8 @@ makecontext, swapcontext \- manipulate user context
 In a System V-like environment, one has the type \fIucontext_t\fP defined in
 .I <ucontext.h>
 and the four functions
-.BR getcontext (2),
-.BR setcontext (2),
+.BR getcontext (3),
+.BR setcontext (3),
 .BR makecontext ()
 and
 .BR swapcontext ()
@@ -45,13 +45,13 @@ that allow user-level context switching
 between multiple threads of control within a process.
 .LP
 For the type and the first two functions, see
-.BR getcontext (2).
+.BR getcontext (3).
 .LP
 The
 .BR makecontext ()
 function modifies the context pointed to
 by \fIucp\fP (which was obtained from a call to
-.BR getcontext (2)).
+.BR getcontext (3)).
 Before invoking
 .BR makecontext (),
 the caller must allocate a new stack
@@ -60,7 +60,7 @@ and define a successor context and
 assign its address to \fIucp\->uc_link\fP.
 
 When this context is later activated (using
-.BR setcontext (2)
+.BR setcontext (3)
 or
 .BR swapcontext ())
 the function \fIfunc\fP is called,
@@ -134,7 +134,7 @@ to permit this on some 64-bit architectures (e.g., x86-64).
 .SH EXAMPLE
 .PP
 The example program below demonstrates the use of
-.BR getcontext (2),
+.BR getcontext (3),
 .BR makecontext (),
 and
 .BR swapcontext ().
@@ -215,8 +215,8 @@ main(int argc, char *argv[])
 }
 .fi
 .SH "SEE ALSO"
-.BR getcontext (2),
 .BR sigaction (2),
 .BR sigaltstack (2),
 .BR sigprocmask (2),
+.BR getcontext (3),
 .BR sigsetjmp (3)