Removed `using std::string`

`using` classes from namespaces can lead to lack of clarity as to where
the class is coming form.
Gif.cpp: removed redundant `using std::min`
DisR5900: removed `using std::string`
Merge pull request #196 from archshift/using

Removed uses of `using std::string`
Remove some horrible old code. Part 1.
Remove some init functions which can be replaced by simple variable init.
Use clz instead of bsr for linux, fix fallback going out of bounds. MSVC still needs help.
Remove cheat patches that were made obsolete in 2010.
Remove redundant code. Horrible old code. Part 2.
Because every programmer needs to redefine min and max.
Clean up intrinsics file with unused code and pre-gcc4.1 fallbacks. Remove some horrible old code. Part 3.
Clean up some code to make it more readable. Even though plugins may be deprecated, clean up/fix bugs there too.