malloc.3: Add some structuring to improve readability

Add some subsection (.SS) headings and paragraph breaks in
DESCRIPTION, to make the page more easily readable.

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

man3/malloc.3

@@ -58,6 +58,7 @@ Feature Test Macro Requirements for glibc (see
         _GNU_SOURCE
 .fi
 .SH DESCRIPTION
+.SS malloc()
 The
 .BR malloc ()
 function allocates
@@ -71,7 +72,7 @@ is 0, then
 returns a unique pointer value that can later be successfully passed to
 .BR free ().
 (See "Nonportable behavior" for portability issues.)
-.PP
+.SS free()
 The
 .BR free ()
 function frees the memory space pointed to by
@@ -85,7 +86,7 @@ has already been freed, undefined behavior occurs.
 If
 .I ptr
 is NULL, no operation is performed.
-.PP
+.SS calloc()
 The
 .BR calloc ()
 function allocates memory for an array of
@@ -102,6 +103,7 @@ is 0, then
 .BR calloc ()
 returns a unique pointer value that can later be successfully passed to
 .BR free ().
+.PP
 If the multiplication of
 .I nmemb
 and
@@ -119,7 +121,7 @@ with the result that an incorrectly sized block of memory would be allocated:
 malloc(nmemb * size);
 .EE
 .in
-.PP
+.SS realloc()
 The
 .BR realloc ()
 function changes the size of the memory block pointed to by
@@ -132,13 +134,15 @@ up to the minimum of the old and new sizes.
 If the new size is larger than the old size, the added memory will
 .I not
 be initialized.
+.PP
 If
 .I ptr
 is NULL, then the call is equivalent to
 .IR malloc(size) ,
 for all values of
-.IR size ;
-if
+.IR size .
+.PP
+If
 .I size
 is equal to zero,
 and
@@ -146,6 +150,7 @@ and
 is not NULL, then the call is equivalent to
 .I free(ptr)
 (but see "Nonportable behavior" for portability issues).
+.PP
 Unless
 .I ptr
 is NULL, it must have been returned by an earlier call to
@@ -154,7 +159,7 @@ or related functions.
 If the area pointed to was moved, a
 .I free(ptr)
 is done.
-.PP
+.SS reallocarray()
 The
 .BR reallocarray ()
 function changes the size of the memory block pointed to by