CALL and RET instructions.

Changed PSHP and POPP into CALL and RET, streamlining their use for subroutine calls.
Updated Assembler and Emulator.
New demonstration programs.

Source/Assembler/assembly.c

@@ -27,6 +27,8 @@ Instruction instruction_set[] = {
     {0x11, "BRQ"},
     {0x12, "BRA"},
     {0x13, "BRB"},
+    {0x14, "CALL"},
+    {0x15, "RET"},
     // Register Operations:
     {0x20, "RSTA"},
     {0x21, "RSTB"},
@@ -42,12 +44,10 @@ Instruction instruction_set[] = {
     {0x30, "PSHQ"},
     {0x31, "PSHA"},
     {0x32, "PSHB"},
-    {0x33, "PSHP"},
-    {0x34, "PSHD"},
-    {0x35, "POPA"},
-    {0x36, "POPB"},
-    {0x37, "POPP"},
-    {0x38, "POPD"},
+    {0x33, "PSHD"},
+    {0x34, "POPA"},
+    {0x35, "POPB"},
+    {0x36, "POPD"},
     // Data Operations:
     {0x40, "INCD"},
     {0x41, "DECD"},