Minor fix in ch02.md and ch03.md (#92)

* Minor fix in ch02.md

* Fixed ref in Listing 3.4 and wrong info in 3.3.1

Author: zylalx1

ch02.md

@@ -341,7 +341,7 @@ FreeRTOS
         ├─[Demo z]  Contains the project file that builds demo 'z'
         └─Common    Contains files that are built by all the demo applications
 ```
-*Figure 2.4 The demo directory hierarchy*
+***Figure 2.4*** *The demo directory hierarchy*
 * * *
 
 

ch03.md

@@ -508,7 +508,7 @@ linker consumes all of RAM1, as shown in Figure 3.4 **C**.
 #define RAM1_HEAP_SIZE ( 30 * 1024 )
 static uint8_t ucHeap[ RAM1_HEAP_SIZE ];
 
-/* Create an array of HeapRegion_t definitions. Whereas in Listing 3.5 the
+/* Create an array of HeapRegion_t definitions. Whereas in Listing 3.3 the
    first entry described all of RAM1, so heap_5 will have used all of
    RAM1, this time the first entry only describes the ucHeap array, so
    heap_5 will only use the part of RAM1 that contains the ucHeap array.
@@ -556,10 +556,9 @@ the array in place of the declaration that would otherwise be in the
 heap\_n.c source file. Declaring the array in the application code
 enables the application writer to specify its start address.
 
-If `configAPPLICATION_ALLOCATED_HEAP` is set to 1 in FreeRTOSConfig.h, or
-left undefined, the application that uses FreeRTOS must allocate a
-`uint8_t` array called `ucHeap` and dimensioned by the `configTOTAL_HEAP_SIZE`
-constant.
+If `configAPPLICATION_ALLOCATED_HEAP` is set to 1 in FreeRTOSConfig.h,
+the application that uses FreeRTOS must allocate a `uint8_t` array
+called `ucHeap` and dimensioned by the `configTOTAL_HEAP_SIZE` constant.
 
 The syntax required to place a variable at a specific memory address is
 dependent on the compiler in use, so refer to your compiler's