[BSP] tm4c129x: fix compile bug when turn RT_USING_LWIP

1. Resize RT_LWIP_SEG_NUM drom 8 to 12
2. modify gcc compile switch, using C99

bsp/tm4c129x/rtconfig.h

@@ -166,7 +166,7 @@
 // </section>
 
 // <section name="RT_USING_LWIP" description="lwip, a lightweight TCP/IP protocol stack" default="true" >
-//#define RT_USING_LWIP
+#define RT_USING_LWIP
 // <bool name="RT_USING_LWIP141" description="Using lwIP 1.4.1 version" default="true" />
 #define RT_USING_LWIP141
 // <bool name="RT_LWIP_ICMP" description="Enable ICMP protocol" default="true" />
@@ -192,7 +192,7 @@
 // <bool name="RT_LWIP_DHCP" description="Enable DHCP client to get IP address" default="false" />
 // #define RT_LWIP_DHCP
 // <integer name="RT_LWIP_TCP_SEG_NUM" description="the number of simultaneously queued TCP" default="4" />
-#define RT_LWIP_TCP_SEG_NUM 8
+#define RT_LWIP_TCP_SEG_NUM 12
 // <integer name="RT_LWIP_TCPTHREAD_PRIORITY" description="the thread priority of TCP thread" default="128" />
 #define RT_LWIP_TCPTHREAD_PRIORITY  12
 // <integer name="RT_LWIP_TCPTHREAD_MBOX_SIZE" description="the mail box size of TCP thread to wait for" default="32" />

bsp/tm4c129x/rtconfig.py

@@ -45,7 +45,7 @@ if PLATFORM == 'gcc':
     OBJCPY = PREFIX + 'objcopy'
 	
     DEVICE = ' -mcpu=cortex-m4 -mthumb -mfpu=fpv4-sp-d16 -mfloat-abi=softfp -ffunction-sections -fdata-sections'
-    CFLAGS = DEVICE + ' -std=gnu11 -Dgcc'
+    CFLAGS = DEVICE + ' -std=c99 -Dgcc'
     AFLAGS = ' -c' + DEVICE + ' -x assembler-with-cpp -Wa,-mimplicit-it=thumb '
     LFLAGS = DEVICE + ' -Wl,--gc-sections,-Map=rtthread-tm4c129x.map,-cref,-u,Reset_Handler -T tm4c_rom.ld'