mmap.2: Minor rewording of MAP_FIXED text

The paragraph break-up of the existing text was
somewhat unnatural.

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

man2/mmap.2

@@ -225,16 +225,16 @@ part of the existing mapping(s) will be discarded.
 If the specified address cannot be used,
 .BR mmap ()
 will fail.
+.IP
 Software that aspires to be portable should use this option with care,
 keeping in mind that the exact layout of a process's memory mappings
 is allowed to change significantly between kernel versions,
 C library versions, and operating system releases.
-.IP
 Furthermore, this option is extremely hazardous (when used on its own),
 because it forcibly removes preexisting mappings,
 making it easy for a multithreaded process to corrupt its own address space.
 .IP
-For example, thread A looks through
+For example, suppose that thread A looks through
 .I /proc/<pid>/maps
 and locates an available address range,
 while thread B simultaneously acquires part or all of that same
@@ -242,12 +242,11 @@ address range.
 Thread A then calls
 .BR mmap(MAP_FIXED) ,
 effectively overwriting the mapping that thread B created.
-.IP
-Thread B need not create a mapping directly; simply making a library call
+In this scenario,
+thread B need not create a mapping directly; simply making a library call
 that, internally, uses
 .BR dlopen (3)
-to load some other shared library, will
-suffice.
+to load some other shared library, will suffice.
 The
 .BR dlopen (3)
 call will map the library into the process's address space.
@@ -261,6 +260,7 @@ Examples include
 and the PAM libraries
 .UR http://www.linux-pam.org
 .UE .
+.IP
 Newer kernels
 (Linux 4.17 and later) have a
 .B MAP_FIXED_NOREPLACE