headers: Fix compile warning: FindResource redefined

Warning is:

    In file included from mingw-w64-headers/include/windows.h:70,
                     from libsrc/dxerr.c:15,
                     from libsrc/dxerr8w.c:20:
    mingw-w64-headers/include/winbase.h:2171: warning: "FindResource" redefined
     #define FindResource __MINGW_NAME_AW(FindResource)

    In file included from mingw-w64-headers/include/winbase.h:24,
                     from mingw-w64-headers/include/windows.h:70,
                     from libsrc/dxerr.c:15,
                     from libsrc/dxerr8w.c:20:
    mingw-w64-headers/include/libloaderapi.h:62: note: this is the location of the previous definition
     #define FindResource FindResourceW

Fix it by conditionally defining FindResource in winbase.h directly as
FindResourceA for non-UNICODE builds and let libloaderapi.h to define
FindResource as FindResourceW for UNICODE builds.

Signed-off-by: LIU Hao <lh_mouse@126.com>
diff --git a/mingw-w64-headers/include/winbase.h b/mingw-w64-headers/include/winbase.h
index 05813b9..f0affe0 100644
--- a/mingw-w64-headers/include/winbase.h
+++ b/mingw-w64-headers/include/winbase.h
@@ -2074,6 +2074,7 @@
 
 #ifndef UNICODE
 #define GetStartupInfo GetStartupInfoA
+#define FindResource FindResourceA
 #define FindResourceEx FindResourceExA
 #define EnumResourceNames EnumResourceNamesA
 #endif
@@ -2167,8 +2168,6 @@
   WINBASEAPI WINBOOL WINAPI SetDllDirectoryA (LPCSTR lpPathName);
   WINBASEAPI WINBOOL WINAPI SetDllDirectoryW (LPCWSTR lpPathName);
   WINBASEAPI HRSRC WINAPI FindResourceW (HMODULE hModule, LPCWSTR lpName, LPCWSTR lpType);
-
-#define FindResource __MINGW_NAME_AW(FindResource)
 #endif
 
 #if WINAPI_FAMILY_PARTITION (WINAPI_PARTITION_DESKTOP) || NTDDI_VERSION >= NTDDI_WIN10_VB