Test for WIN32 instead of __MINGW32_

The code which is conditional on MinGW32 is actually conditional on Windows.
Use the WIN32 symbol, which is defined by the MINGW32 and MSVC environments,
but not by Cygwin.

Signed-off-by: Frank Li <lznuaa@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

help.c

@@ -126,7 +126,7 @@ static int is_executable(const char *name)
 	    !S_ISREG(st.st_mode))
 		return 0;
 
-#ifdef __MINGW32__
+#ifdef WIN32
 {	/* cannot trust the executable bit, peek into the file instead */
 	char buf[3] = { 0 };
 	int n;

run-command.c

@@ -67,7 +67,7 @@ int start_command(struct child_process *cmd)
 
 	trace_argv_printf(cmd->argv, "trace: run_command:");
 
-#ifndef __MINGW32__
+#ifndef WIN32
 	fflush(NULL);
 	cmd->pid = fork();
 	if (!cmd->pid) {
@@ -294,7 +294,7 @@ int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const
 	return run_command(&cmd);
 }
 
-#ifdef __MINGW32__
+#ifdef WIN32
 static __stdcall unsigned run_thread(void *data)
 {
 	struct async *async = data;
@@ -310,7 +310,7 @@ int start_async(struct async *async)
 		return error("cannot create pipe: %s", strerror(errno));
 	async->out = pipe_out[0];
 
-#ifndef __MINGW32__
+#ifndef WIN32
 	/* Flush stdio before fork() to avoid cloning buffers */
 	fflush(NULL);
 
@@ -339,7 +339,7 @@ int start_async(struct async *async)
 
 int finish_async(struct async *async)
 {
-#ifndef __MINGW32__
+#ifndef WIN32
 	int ret = 0;
 
 	if (wait_or_whine(async->pid))

run-command.h

@@ -79,7 +79,7 @@ struct async {
 	int (*proc)(int fd, void *data);
 	void *data;
 	int out;	/* caller reads from here and closes it */
-#ifndef __MINGW32__
+#ifndef WIN32
 	pid_t pid;
 #else
 	HANDLE tid;

setup.c

@@ -41,7 +41,7 @@ const char *prefix_path(const char *prefix, int len, const char *path)
 const char *prefix_filename(const char *pfx, int pfx_len, const char *arg)
 {
 	static char path[PATH_MAX];
-#ifndef __MINGW32__
+#ifndef WIN32
 	if (!pfx || !*pfx || is_absolute_path(arg))
 		return arg;
 	memcpy(path, pfx, pfx_len);