Remove c/winapi and rename some windows types (#5448)

winapi.cr used old and outdated conventions regarding the windows porting
effort. It is deleted, and the definitions in it which are used are moved to
files corresponding to the windows header they are defined in.

Some windows types are also renamed to retain their capitalisation from
Microsoft's headers.

src/lib_c/x86_64-windows-msvc/c/int_safe.cr

@@ -0,0 +1,3 @@
+lib LibC
+  alias DWORD = UInt32
+end

src/lib_c/x86_64-windows-msvc/c/win_nt.cr

@@ -0,0 +1,3 @@
+lib LibC
+  alias LPSTR = Char*
+end

src/lib_c/x86_64-windows-msvc/c/winbase.cr

@@ -0,0 +1,16 @@
+require "c/win_nt"
+require "c/int_safe"
+
+lib LibC
+  fun GetLastError : DWORD
+
+  FORMAT_MESSAGE_ALLOCATE_BUFFER = 0x00000100_u32
+  FORMAT_MESSAGE_IGNORE_INSERTS  = 0x00000200_u32
+  FORMAT_MESSAGE_FROM_STRING     = 0x00000400_u32
+  FORMAT_MESSAGE_FROM_HMODULE    = 0x00000800_u32
+  FORMAT_MESSAGE_FROM_SYSTEM     = 0x00001000_u32
+  FORMAT_MESSAGE_ARGUMENT_ARRAY  = 0x00002000_u32
+
+  fun FormatMessageA(dwFlags : DWORD, lpSource : Void*, dwMessageId : DWORD, dwLanguageId : DWORD,
+                     lpBuffer : LPSTR, nSize : DWORD, arguments : Void*) : DWORD
+end

src/winerror.cr

@@ -1,13 +1,15 @@
+require "c/winbase"
+
 class WinError < Errno
   # NOTE: `get_last_error` must be called BEFORE an instance of this class
   # is malloced as it would change the "last error" to SUCCESS
   def self.new(message)
-    new(message, LibC._GetLastError)
+    new(message, LibC.GetLastError)
   end
 
   def initialize(message, code)
     buffer = uninitialized UInt8[256]
-    size = LibC._FormatMessageA(LibC::FORMAT_MESSAGE_FROM_SYSTEM, nil, code, 0, buffer, buffer.size, nil)
+    size = LibC.FormatMessageA(LibC::FORMAT_MESSAGE_FROM_SYSTEM, nil, code, 0, buffer, buffer.size, nil)
     details = String.new(buffer.to_unsafe, size).strip
     super("#{message}: [WinError #{code}, #{details}]", winerror_to_errno(code))
   end