[MIPS] Add sgidefs.h for mips64

Sgidefs.h is needed by strace.
Replaced now-duplicate arch-mips64/include directory
by symlink to arch-mips/include.

Change-Id: I7808602cfa452eca3ffbdb94903f4c5bdb33efa3

diff --git a/libc/arch-mips64/include b/libc/arch-mips64/include
new file mode 120000 (symlink)
index 0000000..fabbe8a
--- /dev/null
+++ b/libc/arch-mips64/include
@@ -0,0 +1 @@
+../arch-mips/include
\ No newline at end of file

diff --git a/libc/arch-mips64/include/machine b/libc/arch-mips64/include/machine
deleted file mode 120000 (symlink)
index 36466ee..0000000
--- a/libc/arch-mips64/include/machine
+++ /dev/null
@@ -1 +0,0 @@
-../../arch-mips/include/machine
\ No newline at end of file