Shorten GPIO and USART initial code

1. Merge set GPIO_Pin_3 initial code into "set (*(uint32_t *)$osp) = 0x04000008",
   where GPIO_Pin_3 = (uint16_t) 0x0008 and GPIO_Mode_IN_FLOATING = 0x04

2. Merge set GPIO_Pin 2 initial code into "set (*(uint32_t *)$osp) = 0x18030004",
   where GPIO_Pin_2 = (uint16_t) 0x0004, GPIO_Speed_50MHz = 3 and
   GPIO_Mode_AF_PP = 0x18

3. Shorten USART initial code by calling "USART_StructInit($osp)"

4. Remove USART_SendData Hello
Add 'tags' into .gitignore
Merge USART SendData Hello

By using while loop in gdb.in.