refactor to use new errno path

Author: michaelrj-google

libc/src/stdio/generic/perror.cpp

@@ -10,8 +10,8 @@
 #include "src/__support/CPP/string_view.h"
 #include "src/__support/File/file.h"
 #include "src/__support/StringUtil/error_to_string.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
-#include "src/errno/libc_errno.h"
 
 namespace LIBC_NAMESPACE_DECL {
 

libc/test/src/stdio/perror_test.cpp

@@ -8,7 +8,7 @@
 
 #include "src/stdio/perror.h"
 
-#include "src/errno/libc_errno.h"
+#include "src/__support/libc_errno.h"
 #include "test/UnitTest/Test.h"
 
 // The standard says perror prints directly to stderr and returns nothing. This