Make the compiler/ar/linker file output parameters overrideable

This is in preparation for allowing building using MSVC via
makefiles.
Allow overriding the command syntax for linking libraries
Allow overriding the cflags for debug/optimization and for 32/64 bit
Add platform files for msvc and msvc-arm

Build with "make UNAME=msvc" to invoke this.
Don't load welsdec.dll at runtime in the decConsole test app on windows

Instead just link directly to it. This matches how the library is
linked/loaded in encConsole/h264enc as well.

Only the 2008 version project file is updated for now, since
the 2010 and 2012 ones are out of sync right now.
Merge pull request #150 from mstorsjo/msvc-make

Support building with MSVC via the makefiles by doing "make UNAME=msvc"