builtin: declare fn C._vinit/2 and fn C._vcleanup/0 (continuation from #23812) (#23820)

vlib/builtin/builtin.c.v

@@ -6,6 +6,12 @@ pub type FnExitCb = fn ()
 fn C.atexit(f FnExitCb) int
 fn C.strerror(int) &char
 
+// These functions (_vinit, and _vcleanup), are generated by V, and if you have a `module no_main` program,
+// you should ensure to call them when appropriate.
+fn C._vinit(argc int, argv &&char)
+
+fn C._vcleanup()
+
 @[markused]
 fn v_segmentation_fault_handler(signal_number i32) {
 	$if freestanding {

vlib/builtin/builtin_windows.c.v

@@ -7,6 +7,8 @@ module builtin
 // g_original_codepage - used to restore the original windows console code page when exiting
 __global g_original_codepage = u32(0)
 
+// See https://learn.microsoft.com/en-us/windows/win32/winprog/windows-data-types
+// See https://www.codeproject.com/KB/string/cppstringguide1.aspx
 pub type C.BOOL = int
 
 pub type C.HINSTANCE = voidptr
@@ -25,6 +27,20 @@ pub type C.HANDLE = voidptr
 
 pub type C.LRESULT = voidptr
 
+pub type C.CHAR = char
+
+pub type C.TCHAR = u16 // It is u8 if UNICODE is not defined, but for V programs it always is
+
+pub type C.WCHAR = u16
+
+pub type C.LPSTR = &char
+
+pub type C.LPWSTR = &C.WCHAR
+
+pub type C.LPTSTR = &C.TCHAR
+
+pub type C.LPCTSTR = &C.TCHAR
+
 // utf8 to stdout needs C.SetConsoleOutputCP(cp_utf8)
 fn C.GetConsoleOutputCP() u32
 

vlib/v/tests/create_dll/create_win_dll.c.v

@@ -1,6 +1,5 @@
 module test
 
-fn C._vinit(int, voidptr)
 fn C.GC_INIT()
 
 const foo = 1