Add support for the ARM IPSR register. (#1067)

1. Create an enum name for the IPSR register.
2. Implement read and write of the IPSR via the xpsr helper functions.

Fixes #1065

include/unicorn/arm.h

@@ -133,6 +133,7 @@ typedef enum uc_arm_reg {
     UC_ARM_REG_C13_C0_2,
     UC_ARM_REG_C13_C0_3,
 
+    UC_ARM_REG_IPSR,
     UC_ARM_REG_ENDING,		// <-- mark the end of the list or registers
 
     //> alias registers