add LWQQ_EXPORT for win dll export

Signed-off-by: xiehuc <xiehuc@gmail.com>
add xcode project

Signed-off-by: xiehuc <xiehuc@gmail.com>
fix a wrong header including

Signed-off-by: xiehuc <xiehuc@gmail.com>
add macro settings for poll msg

Signed-off-by: xiehuc <xiehuc@gmail.com>
add version macro

Signed-off-by: xiehuc <xiehuc@gmail.com>
static link on windows

Signed-off-by: xiehuc <xiehuc@gmail.com>
only include lwqq_export.h on windows

似乎在2.8.x中不能够顺利的生成lwqq_export.h文件. 在linux等系统上并不需要
该文件. 所以不必包含.

Signed-off-by: xiehuc <xiehuc@gmail.com>