Apply touchups to last PR

Compilers like GCC require comments on lines like `#endif rdmsr`. Since
the rdmsr macro was only being used in arch_prctl(), I've localized the
macro, and I'm considering deleting arch_prctl() too, since there isn't
any way to have mem segments unfortunately across operating systems ;_;
The remaining changed lines are due to clang-format which runs on auto.

ape/lib/pageunmap.c

@@ -17,11 +17,10 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "ape/lib/pc.h"
-#include "libc/bits/bits.h"
 
 textreal void pageunmap(int64_t vaddr) {
   uint64_t *entry;
   entry = __getpagetableentry(vaddr, 3, &g_pml4t, &g_ptsp_xlm);
   *entry &= ~PAGE_V;
-  invlpg(vaddr);
+  asm volatile("invlpg\t(%0)" : /* no outputs */ : "r"(vaddr) : "memory");
 }