[README] Coarse sweep to use markup in READMEs.

This should improve online readability of the readme files.

examples/stm32/l1/stm32l-discovery/usart-semihosting/README.md

@@ -1,6 +1,4 @@
-------------------------------------------------------------------------------
-README
-------------------------------------------------------------------------------
+# README
 
 This example program sends some characters on USART2 on the
 ST STM32L DISCOVERY eval board. (USART2 TX on PA2 @ 115200 8n1)
@@ -12,45 +10,45 @@ https://launchpad.net/gcc-arm-embedded
 Semihosting is a neat feature, but remember that your application will
 NOT WORK standalone if you have semihosting turned on!
 
-$ make ENABLE_SEMIHOSTING=0 will rebuild this image _without_ semihosting
+    $ make ENABLE_SEMIHOSTING=0 will rebuild this image _without_ semihosting
 
 Semihosting is supported in "recent"[1] OpenOCD versions, however, you need
 to enable semihosting first!  If you have not enabled semihosting, you
 will receive a message like this:
 
-(gdb) run
-The program being debugged has been started already.
-Start it from the beginning? (y or n) y
-
-Starting program:
-/home/karlp/src/libopencm3-examples/examples/stm32/l1/stm32l-discovery/usart-semihosting/usart-semihosting.elf 
-
-Program received signal SIGTRAP, Trace/breakpoint trap.
-0x08000456 in initialise_monitor_handles ()
-(gdb)
-
-# Here we enable semi-hosting
-
-(gdb) mon arm semihosting enable
-semihosting is enabled
-(gdb) continue
-...
+    (gdb) run
+    The program being debugged has been started already.
+    Start it from the beginning? (y or n) y
+    
+    Starting program:
+    /home/karlp/src/libopencm3-examples/examples/stm32/l1/stm32l-discovery/usart-semihosting/usart-semihosting.elf 
+    
+    Program received signal SIGTRAP, Trace/breakpoint trap.
+    0x08000456 in initialise_monitor_handles ()
+    (gdb)
+    
+    # Here we enable semi-hosting
+    
+    (gdb) mon arm semihosting enable
+    semihosting is enabled
+    (gdb) continue
+    ...
 
 You should now see the semihosting output in the window running OpenOCD.
 
-Size Notes
-~~~~~~~~~~
+## Size Notes
+
 Semihosting is basically free
 
-# Without
-$ arm-none-eabi-size usart-semihosting.elf 
-   text	   data	    bss	    dec	    hex	filename
-  29056	   2212	     60	  31328	   7a60	usart-semihosting.elf
+### Without
+    $ arm-none-eabi-size usart-semihosting.elf 
+       text	   data	    bss	    dec	    hex	filename
+      29056	   2212	     60	  31328	   7a60	usart-semihosting.elf
 
-# With
-$ arm-none-eabi-size usart-semihosting.elf 
-   text	   data	    bss	    dec	    hex	filename
-  29832	   2212	    232	  32276	   7e14	usart-semihosting.elf
+### With
+    $ arm-none-eabi-size usart-semihosting.elf 
+       text	   data	    bss	    dec	    hex	filename
+      29832	   2212	    232	  32276	   7e14	usart-semihosting.elf
 
 The large size here is because of printf being included regardless, see
 nano.specs if you care about this, this data here is to show that semihosting