Ensure Python is available before trying to run gen_x86_insn.py.

Use registry key search to avoid version/location dependency.

Noticed by: Brian Gladman  <brg@gladman.plus.com>

svn path=/trunk/yasm/; revision=1957

Mkfiles/vc/genperf/run.bat

@@ -1,5 +1,18 @@
 cd ..\..\..
+@echo off
+reg query HKCR\Python.File\shell\open\command >nul: 2>&1
+goto answer%errorlevel%
+:answer0
+echo Python found!
+@echo on
 modules\arch\x86\gen_x86_insn.py
+@echo off
+goto end
+:answer1
+echo Python not found!
+goto end
+:end
+@echo on
 %1 x86insn_nasm.gperf x86insn_nasm.c
 %1 x86insn_gas.gperf x86insn_gas.c
 %1 modules\arch\x86\x86cpu.gperf x86cpu.c

Mkfiles/vc8/genperf/run.bat

@@ -1,5 +1,18 @@
 cd ..\..\..
+@echo off
+reg query HKCR\Python.File\shell\open\command >nul: 2>&1
+goto answer%errorlevel%
+:answer0
+echo Python found!
+@echo on
 modules\arch\x86\gen_x86_insn.py
+@echo off
+goto end
+:answer1
+echo Python not found!
+goto end
+:end
+@echo on
 %1 x86insn_nasm.gperf x86insn_nasm.c
 %1 x86insn_gas.gperf x86insn_gas.c
 %1 modules\arch\x86\x86cpu.gperf x86cpu.c