asm: start x86 intrinsics examples

Split userland/arch/<arch>/c/ into inline_asm and intrinsics, and move programs
that don't match either up.

userland/arch/x86_64/binutils_hack.c

@@ -0,0 +1,20 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#your-first-binutils-hack */
+
+#include <assert.h>
+#include <inttypes.h>
+
+int main(void) {
+#if 0
+    uint64_t in = 0xFFFFFFFF;
+    uint64_t out = 0;
+    __asm__ (
+        "mov %[in], %%rax;"
+        "myinc %%rax;"
+        "movq %%rax, %[out]"
+        : [out] "=g" (out)
+        : [in] "g" (in)
+        : "rax"
+    );
+    assert(out == in + 1);
+#endif
+}