clone.2: Add information about clone and clone2 on IA-64

Note that clone() definition on IA-64 is the same as on
SH/Tile/Alpha, align __clone2 declarations in line with the
previous ones, add clone2 syscall prototype.

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

man2/clone.2

@@ -867,7 +867,7 @@ and there are variations in the arguments across architectures,
 as detailed in the following paragraphs.
 .PP
 The raw system call interface on x86-64 and some other architectures
-(including sh, tile, and alpha) is:
+(including sh, tile, ia-64, and alpha) is:
 .PP
 .in +4
 .EX
@@ -926,24 +926,29 @@ For details, see the kernel (and glibc) source.
 .SS ia64
 On ia64, a different interface is used:
 .PP
-.nf
+.in +4
+.EX
 .BI "int __clone2(int (*" "fn" ")(void *), "
 .BI "             void *" child_stack_base ", size_t " stack_size ,
 .BI "             int " flags ", void *" "arg" ", ... "
 .BI "          /* pid_t *" ptid ", struct user_desc *" tls \
 ", pid_t *" ctid " */ );"
-.fi
+.EE
+.in
 .PP
-The prototype shown above is for the glibc wrapper function;
+The prototype shown above is for the glibc wrapper function; for the syscall
-the raw system call interface has no
+itself, prototype can be described as follows (it is identical to the
-.I fn
+.BR clone ()
-or
+prototype on microblaze):
-.I arg
+.PP
-argument, and changes the order of the arguments so that
+.in +4
-.I flags
+.EX
-is the first argument, and
+.BI "long clone2(unsigned long " flags ", void *" child_stack_base ,
-.I tls
+.BI "            int " stack_size , "\fR         /* Size of stack */"
-is the last argument.
+.BI "            int *" ptid ", int *" ctid ,
+.BI "            unsigned long " tls );
+.EE
+.in
 .PP
 .BR __clone2 ()
 operates in the same way as