Add unused but required vectorPermute pcodeop (#82)

This, including the comment, is copied from Ghidra's PPC definitions.
Without the vectorPermute pcodeop defined, the
PPCEmulateInstructionStateModifier class produces an exception, breaking
all Ghidra functionality that depends on pcode emulation.

data/languages/ppc_gekko_broadway.slaspec

@@ -799,6 +799,10 @@ define pcodeop TLBWrite;
 define pcodeop WriteExternalEnable;
 define pcodeop WriteExternalEnableImmediate;
 
+# This is really used in the altivec version, but since it's a registered pcode op
+# and due to the way things get @included, this needs to be here
+define pcodeop vectorPermute;
+
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 # Macros
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