syscall organization overhaul

now public syscall.h only exposes __NR_* and SYS_* constants and the
variadic syscall function. no macros or inline functions, no
__syscall_ret or other internal details, no 16-/32-bit legacy syscall
renaming, etc. this logic has all been moved to src/internal/syscall.h
with the arch-specific parts in arch/$(ARCH)/syscall_arch.h, and the
amount of arch-specific stuff has been reduced to a minimum.

changes still need to be reviewed/double-checked. minimal testing on
i386 and mips has already been performed.

arch/arm/syscall_arch.h

@@ -0,0 +1,41 @@
+#define __SYSCALL_LL_E(x) \
+((union { long long ll; long l[2]; }){ .ll = x }).l[0], \
+((union { long long ll; long l[2]; }){ .ll = x }).l[1]
+#define __SYSCALL_LL_O(x) 0, __SYSCALL_LL_E((x))
+
+#define __SYSCALL_SSLEN 8
+
+static inline long __syscall0(long n)
+{
+	return (__syscall)(n);
+}
+
+static inline long __syscall1(long n, long a)
+{
+	return (__syscall)(n, a);
+}
+
+static inline long __syscall2(long n, long a, long b)
+{
+	return (__syscall)(n, a, b);
+}
+
+static inline long __syscall3(long n, long a, long b, long c)
+{
+	return (__syscall)(n, a, b, c);
+}
+
+static inline long __syscall4(long n, long a, long b, long c, long d)
+{
+	return (__syscall)(n, a, b, c, d);
+}
+
+static inline long __syscall5(long n, long a, long b, long c, long d, long e)
+{
+	return (__syscall)(n, a, b, c, d, e);
+}
+
+static inline long __syscall6(long n, long a, long b, long c, long d, long e, long f)
+{
+	return (__syscall)(n, a, b, c, d, e, f);
+}