lstrcat，连结两个LPTSTR 字符串

LPCSTR :指向一个字符串常量的指针（每个字符是占一个字节）
LPCTSTR　：指向一个字符串常量的指针（每个字符是占两个字节）
LPTSTR　：指向一个字符串的指针（每个字符是占两个字节）

LPTSTR lstrcat(
LPTSTR lpString1,
LPTSTR lpString2
);
Parameters:
lpString1
[in, out] Pointer to a null-terminated string. The buffer must be large enough to contain both strings.
lpString2
[in] Pointer to the null-terminated string to be appended to the string specified in the lpString1 parameter.

Return Value:
If the function succeeds, the return value is a pointer to the buffer.
If the function fails, the return value is NULL and lpString1 may not be null-terminated.