Lift a lot of stuff out of HPHP::VM.

This is a partial step towards merging the HPHP::VM namespace
up into its parent. To keep it reviewable/mergeable I'm not doing
everything at once here, but most of the code I've touched seems
improved. I've drawn an invisible line around the jit, Unit and
its cohort (Class, Func, PreClass, etc.); we'll get back to them
soon.

hphp/runtime/base/array/hphp_array.cpp

@@ -31,7 +31,7 @@
 #include <util/util.h>
 #include <runtime/base/execution_context.h>
 #include <runtime/vm/member_operations.h>
-#include <runtime/vm/stats.h>
+#include <runtime/base/stats.h>
 
 // If PEDANTIC is defined, extra checks are performed to ensure correct
 // function even as an array approaches 2^31 elements.  In practice this is
@@ -500,7 +500,7 @@ ssize_t /*ElmInd*/ HphpArray::find(int64_t ki) const {
     // Try to get at it without dirtying a data cache line.
     Elm* e = m_data + uint64_t(ki);
     if (e->data.m_type != HphpArray::KindOfTombstone && hitIntKey(e, ki)) {
-      VM::Stats::inc(VM::Stats::HA_FindIntFast);
+      Stats::inc(Stats::HA_FindIntFast);
       assert([&] {
           // Our results had better match the other path
           FIND_BODY(ki, hitIntKey(&elms[pos], ki));
@@ -508,7 +508,7 @@ ssize_t /*ElmInd*/ HphpArray::find(int64_t ki) const {
       return ki;
     }
   }
-  VM::Stats::inc(VM::Stats::HA_FindIntSlow);
+  Stats::inc(Stats::HA_FindIntSlow);
   FIND_BODY(ki, hitIntKey(&elms[pos], ki));
 }