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/arm/inline_asm/inc_memory.c

@@ -0,0 +1,34 @@
+/* Like inc.c but less good since we do more work ourselves.
+ *
+ * Just doing this to test out the "m" memory constraint.
+ *
+ * GCC 8.2.0 -O0 assembles ldr line to:
+ *
+ * ....
+ * ldr r0, [fp, #-12]
+ * ....
+ *
+ * and `-O3` assembles to:
+ *
+ * ....
+ * ldr r0, [sp]
+ * ....
+ *
+ * https://github.com/cirosantilli/linux-kernel-module-cheat#gcc-inline-assembly
+ */
+
+#include <assert.h>
+#include <inttypes.h>
+
+int main(void) {
+    uint32_t my_local_var = 1;
+    __asm__ (
+        "ldr r0, %[my_local_var];"
+        "add r0, r0, #1;"
+        "str r0, %[my_local_var];"
+        : [my_local_var] "+m" (my_local_var)
+        :
+        : "r0"
+    );
+    assert(my_local_var == 2);
+}