Implement getrandom syscall decoding

* getrandom.c: New file.
* Makefile.am (strace_SOURCES): Add it.
* linux/dummy.h (sys_getrandom): Remove.
* linux/syscall.h (sys_getrandom): New prototype.
* xlat/getrandom_flags.in: New file.
* tests/getrandom.c: New file.
* tests/getrandom.awk: New file.
* tests/getrandom.test: New test.
* tests/Makefile.am (check_PROGRAMS): Add getrandom.
(TESTS): Add getrandom.test.
(EXTRA_DIST): Add getrandom.awk.
* tests/.gitignore: Add getrandom.
diff --git a/linux/dummy.h b/linux/dummy.h
index 576fede..85dd060 100644
--- a/linux/dummy.h
+++ b/linux/dummy.h
@@ -34,7 +34,6 @@
 /* still unfinished */
 #define	sys_bpf			printargs
 #define	sys_execveat		printargs
-#define	sys_getrandom		printargs
 #define	sys_ioperm		printargs
 #define	sys_iopl		printargs
 #define	sys_kcmp		printargs
diff --git a/linux/syscall.h b/linux/syscall.h
index d353f74..ba585b3 100644
--- a/linux/syscall.h
+++ b/linux/syscall.h
@@ -104,6 +104,7 @@
 int sys_getitimer();
 int sys_getpmsg(); /* TODO: non-Linux, remove? */
 int sys_getpriority();
+int sys_getrandom();
 int sys_getresuid();
 int sys_getrlimit();
 int sys_getrusage();