Add ARM MSP, PSP and CONTROL register access (#1071)

Necessary for NVIC exception emulation from user.

include/unicorn/arm.h

@@ -134,6 +134,9 @@ typedef enum uc_arm_reg {
     UC_ARM_REG_C13_C0_3,
 
     UC_ARM_REG_IPSR,
+    UC_ARM_REG_MSP,
+    UC_ARM_REG_PSP,
+    UC_ARM_REG_CONTROL,
     UC_ARM_REG_ENDING,		// <-- mark the end of the list or registers
 
     //> alias registers