truss: Add support for fsync(2) and fdatasync(2).

The default handling showed the argument as hex.  Add explicit handling so
we can show it as decimal, since that's how we show file descriptors
everywhere else.

Approved by:	mjg (mentor)
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D19295

usr.bin/truss/syscalls.c

@@ -231,6 +231,8 @@ static struct syscall decoded_syscalls[] = {
 		    { Atflags, 4 } } },
 	{ .name = "fcntl", .ret_type = 1, .nargs = 3,
 	  .args = { { Int, 0 }, { Fcntl, 1 }, { Fcntlflag, 2 } } },
+	{ .name = "fdatasync", .ret_type = 1, .nargs = 1,
+	  .args = { { Int, 0 } } },
 	{ .name = "flock", .ret_type = 1, .nargs = 2,
 	  .args = { { Int, 0 }, { Flockop, 1 } } },
 	{ .name = "fstat", .ret_type = 1, .nargs = 2,
@@ -240,6 +242,8 @@ static struct syscall decoded_syscalls[] = {
 		    { Atflags, 3 } } },
 	{ .name = "fstatfs", .ret_type = 1, .nargs = 2,
 	  .args = { { Int, 0 }, { StatFs | OUT, 1 } } },
+	{ .name = "fsync", .ret_type = 1, .nargs = 1,
+	  .args = { { Int, 0 } } },
 	{ .name = "ftruncate", .ret_type = 1, .nargs = 2,
 	  .args = { { Int | IN, 0 }, { QuadHex | IN, 1 } } },
 	{ .name = "futimens", .ret_type = 1, .nargs = 2,