madvise.2: ffix: Add some paragraph breaks in descriptions of 'advice'

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

man2/madvise.2

@@ -159,6 +159,7 @@ processes.
 This operation may result in the calling process receiving a
 .B SIGBUS
 and the page being unmapped.
+
 This feature is intended for testing of memory error-handling code;
 it is available only if the kernel was configured with
 .BR CONFIG_MEMORY_FAILURE .
@@ -178,6 +179,7 @@ The effect of the
 .B MADV_SOFT_OFFLINE
 operation is invisible to (i.e., does not change the semantics of)
 the calling process.
+
 This feature is intended for testing of memory error-handling code;
 it is available only if the kernel was configured with
 .BR CONFIG_MEMORY_FAILURE .
@@ -195,12 +197,14 @@ These are replaced by a single write-protected page (which is automatically
 copied if a process later wants to update the content of the page).
 KSM merges only private anonymous pages (see
 .BR mmap (2)).
+
 The KSM feature is intended for applications that generate many
 instances of the same data (e.g., virtualization systems such as KVM).
 It can consume a lot of processing power; use with care.
 See the Linux kernel source file
 .I Documentation/vm/ksm.txt
 for more details.
+
 The
 .BR MADV_MERGEABLE
 and
@@ -232,6 +236,7 @@ to replace them with huge pages.
 The kernel will also allocate huge pages directly when the region is
 naturally aligned to the huge page size (see
 .BR posix_memalign (2)).
+
 This feature is primarily aimed at applications that use large mappings of
 data and access large regions of that memory at a time (e.g., virtualization
 systems such as QEMU).
@@ -240,6 +245,7 @@ It can very easily waste memory (e.g., a 2MB mapping that only ever accesses
 See the Linux kernel source file
 .I Documentation/vm/transhuge.txt
 for more details.
+
 The
 .BR MADV_HUGEPAGE
 and