Fix for DEP compatibility (Data Execution Prevention)

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The unit does not work on operating systems where DEP is enabled by default. 
That's because the dll is loaded into non-executable memory areas. 

Fixing this issue is easy: 
In all VirtualAlloc() calls, replace the "PAGE_READWRITE" constant by 
"PAGE_EXECUTE_READWRITE". That means: replace "PAGE_READWRITE" by 
"PAGE_EXECUTE_READWRITE" everywhere in the file except the occurence in the 
GetSectionProtection() function. 

Original issue reported on code.google.com by mabaha...@gmail.com on 10 Nov 2014 at 9:26