incorporate Tony's patches:

+ c/src/lib/libc/support/generic/malloc.c did not initialize the
    sbrk amount
  + _Thread_Handler in c/src/exec/rtems/thread.c left a window
    during the begin extension which could result in a context switch

fixed places which did not correctly distinguish between an
CPU_isr and a CPU_isr_entry.

c/src/lib/libc/malloc.c

@@ -62,6 +62,7 @@ void RTEMS_Malloc_Initialize(
    */
 
   starting_address = start;
+  RTEMS_Malloc_Sbrk_amount = sbrk_amount;
 
   if (!starting_address) {
     u32_address = (unsigned int)sbrk(length);