getpriority.2: NOTES: add "C library/kernel ABI differences" subheading

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

man2/getpriority.2

@@ -198,6 +198,19 @@ Linux before 1.3.36 had \-infinity..15.
 Since kernel 1.3.43, Linux has the range \-20..19.
 On some other systems, the range of nice values is \-20..20.
 
+Including
+.I <sys/time.h>
+is not required these days, but increases portability.
+(Indeed,
+.I <sys/resource.h>
+defines the
+.I rusage
+structure with fields of type
+.I struct timeval
+defined in
+.IR <sys/time.h> .)
+.\"
+.SS C library/kernel ABI differences
 Within the kernel, nice values are actually represented
 using the corresponding range 40..1
 (since negative numbers are error codes) and these are the values
@@ -210,18 +223,6 @@ The glibc wrapper functions for these system calls handle the
 translations between the user-land and kernel representations
 of the nice value according to the formula
 .IR "unice\ =\ 20\ \-\ knice" .
-.LP
-Including
-.I <sys/time.h>
-is not required these days, but increases portability.
-(Indeed,
-.I <sys/resource.h>
-defines the
-.I rusage
-structure with fields of type
-.I struct timeval
-defined in
-.IR <sys/time.h> .)
 .SH BUGS
 According to POSIX, the nice value is a per-process setting.
 However, under the current Linux/NPTL implementation of POSIX threads,