libcgo: set g, m in thread local storage for windows 386.

R=rsc
CC=golang-dev, vcc
https://golang.org/cl/2216051

src/libcgo/windows_386.c

@@ -40,6 +40,16 @@ threadentry(void *v)
 	 */
 	ts.g->stackguard = (uintptr)&ts - ts.g->stackguard + 4096;
 
+	/*
+	 * Set specific keys in thread local storage.
+	 */
+	asm volatile (
+		"MOVL %%fs:0x2c, %%eax\n"	// MOVL 0x24(FS), tmp
+		"movl %0, 0(%%eax)\n"	// MOVL g, 0(FS)
+		"movl %1, 4(%%eax)\n"	// MOVL m, 4(FS)
+		:: "r"(ts.g), "r"(ts.m) : "%eax"
+	);
+	
 	crosscall_386(ts.fn);
 	return nil;
 }