win32: update build instructions with correct CRT version
As stated in http://msdn.microsoft.com/en-us/library/
cc664727.aspx, when you
compile an application with MSVC 2008 SP1 it is bound by default to the
original CRT version (9.0.21022.8). This is the case for Python 2.6 up to 3.1.
If the wrong CRT version is embedded in the Inno Setup installer, with a PC
that does not have the MSVC 2008 redistributable package installed, hg will
refuse to launch with an error: "the system cannot execute the specified
program".