Move ThreadName.cpp macro defs outside C++ section

Summary: [Folly] Move `ThreadName.cpp` macro defs outside C++ section, including outside `namespace ...` blocks.

Reviewed By: vitaut

Differential Revision: D17868541

fbshipit-source-id: a0964ce1f1c6322185f94b8162df4c0e6eaa84bf

folly/system/ThreadName.cpp

@@ -23,8 +23,6 @@
 #include <folly/portability/PThread.h>
 #include <folly/portability/Windows.h>
 
-namespace folly {
-
 // This looks a bit weird, but it's necessary to avoid
 // having an undefined compiler function called.
 #if defined(__GLIBC__) && !defined(__APPLE__) && !defined(__ANDROID__)
@@ -54,6 +52,8 @@ namespace folly {
 #define FOLLY_HAS_PTHREAD_SETNAME_NP_NAME 0
 #endif // defined(__APPLE__)
 
+namespace folly {
+
 namespace {
 
 #if FOLLY_HAVE_PTHREAD && !defined(_WIN32)