minor updates and fixes for building 7-Zip

- add appveyor.cmd for building @ Appveyor
- add build-ia64.cmd for building ia64
- remove package.cmd

CPP/build-x64.cmd

@@ -1,12 +1,16 @@
 @echo on
 
 set ROOT=%cd%\7zip
-set OUTDIR=%ROOT%\bin64
+if not defined OUTDIR set OUTDIR=%ROOT%\bin64
 mkdir %OUTDIR%
 
 set OPTS=CPU=AMD64 MY_STATIC_LINK=1
 set LFLAGS=/SUBSYSTEM:WINDOWS,"5.02"
 
+cd %ROOT%\Bundles\Format7zExtract
+nmake %OPTS%
+copy AMD64\7zxa.dll %OUTDIR%\7zxa.dll
+
 cd %ROOT%\Bundles\Format7z
 nmake %OPTS%
 copy AMD64\7za.dll %OUTDIR%\7za.dll