Fix build for mingw.

Summary: I was building lldb using cross mingw-w64 toolchain on Linux and observed some issues. This is first patch in the series to fix that build. It mostly corrects the case of include files and adjusts some #ifdefs from _MSC_VER to _WIN32 and vice versa. I built lldb on windows with VS after applying this patch to make sure it does not break the build there.

Reviewers: zturner, labath, abidh

Subscribers: ki.stfu, mgorny, lldb-commits

Differential Revision: https://reviews.llvm.org/D27759

llvm-svn: 289821
diff --git a/lldb/source/Core/Mangled.cpp b/lldb/source/Core/Mangled.cpp
index 30c4ac1..c2c63b6 100644
--- a/lldb/source/Core/Mangled.cpp
+++ b/lldb/source/Core/Mangled.cpp
@@ -9,9 +9,9 @@
 
 // FreeBSD9-STABLE requires this to know about size_t in cxxabi.h
 #include <cstddef>
-#if defined(_MSC_VER)
+#if defined(_WIN32)
 #include "lldb/Host/windows/windows.h"
-#include <Dbghelp.h>
+#include <dbghelp.h>
 #pragma comment(lib, "dbghelp.lib")
 #endif