[scudo] Allow for non-Android Shared TSD platforms, part 1

Summary:
This first part just prepares the grounds for part 2 and doesn't add any new
functionality. It mostly consists of small refactors:
- move the `pthread.h` include higher as it will be used in the headers;
- use `errno.h` in `scudo_allocator.cpp` instead of the sanitizer one, update
  the `errno` assignments accordingly (otherwise it creates conflicts on some
  platforms due to `pthread.h` including `errno.h`);
- introduce and use `getCurrentTSD` and `setCurrentTSD` for the shared TSD
  model code;

Reviewers: alekseyshl

Reviewed By: alekseyshl

Subscribers: llvm-commits, srhines

Differential Revision: https://reviews.llvm.org/D38826

llvm-svn: 315583
diff --git a/compiler-rt/lib/scudo/scudo_allocator.cpp b/compiler-rt/lib/scudo/scudo_allocator.cpp
index 077d577..472017d 100644
--- a/compiler-rt/lib/scudo/scudo_allocator.cpp
+++ b/compiler-rt/lib/scudo/scudo_allocator.cpp
@@ -22,9 +22,9 @@
 
 #include "sanitizer_common/sanitizer_allocator_checks.h"
 #include "sanitizer_common/sanitizer_allocator_interface.h"
-#include "sanitizer_common/sanitizer_errno.h"
 #include "sanitizer_common/sanitizer_quarantine.h"
 
+#include <errno.h>
 #include <string.h>
 
 namespace __scudo {
@@ -640,7 +640,7 @@
 void *scudoPvalloc(uptr Size) {
   uptr PageSize = GetPageSizeCached();
   if (UNLIKELY(CheckForPvallocOverflow(Size, PageSize))) {
-    errno = errno_ENOMEM;
+    errno = ENOMEM;
     return Instance.handleBadRequest();
   }
   // pvalloc(0) should allocate one page.
@@ -650,7 +650,7 @@
 
 void *scudoMemalign(uptr Alignment, uptr Size) {
   if (UNLIKELY(!IsPowerOfTwo(Alignment))) {
-    errno = errno_EINVAL;
+    errno = EINVAL;
     return Instance.handleBadRequest();
   }
   return SetErrnoOnNull(Instance.allocate(Size, Alignment, FromMemalign));
@@ -659,18 +659,18 @@
 int scudoPosixMemalign(void **MemPtr, uptr Alignment, uptr Size) {
   if (UNLIKELY(!CheckPosixMemalignAlignment(Alignment))) {
     Instance.handleBadRequest();
-    return errno_EINVAL;
+    return EINVAL;
   }
   void *Ptr = Instance.allocate(Size, Alignment, FromMemalign);
   if (UNLIKELY(!Ptr))
-    return errno_ENOMEM;
+    return ENOMEM;
   *MemPtr = Ptr;
   return 0;
 }
 
 void *scudoAlignedAlloc(uptr Alignment, uptr Size) {
   if (UNLIKELY(!CheckAlignedAllocAlignmentAndSize(Alignment, Size))) {
-    errno = errno_EINVAL;
+    errno = EINVAL;
     return Instance.handleBadRequest();
   }
   return SetErrnoOnNull(Instance.allocate(Size, Alignment, FromMalloc));