Update Windows build to MinGW-w64 4.9.1

Since different versions of MinGW-w64 differ in support of clock-related
functions, we do now suggest using version 4.9.1 which was tested on
several Windows systems.

This fix removes the now obsolete redefinitions of unsupported clock
features and gives detailed instructions in the README for fetching the
correct version of MinGW for Windows builds.
Cut down on automatic header inclusion on Windows

This will prevent windows.h from dragging in lots of other header files
by default. It helps us avoid problems such as having to include
winsock2.h before windows.h which would otherwise lead to problems with
redefined symbols.
Remove -fPIC for builds on Windows

We recommend using MinGW-w64 for the Windows builds which generates
position-independent code by default. Removing the -fPIC option gets
rid of the warning that reminds of this behaviour.
Fix weird numbering in Windows README file
Remove hh modifier from format strings

MinGW does not support C99's hh modifier in format strings (likely for
compatibility with Microsoft's compiler). This fix replaces the modifier
with a cast of char arguments to unsigned char to achieve the same result.
- Fixed a bug where psmove_3axisvector_min() returned the z-axis as the minimum when the y-axis was expected
- Fixed a bug where psmove_3axisvector_max() returned the z-axis as the maximum when the y-axis was expected
Merge pull request #136 from nitsch/fix-windows-build

Fix Windows build
Merge pull request #140 from sivyr/master

Fixed a bug affecting min/max vector computations
Automatically detect BlueZ 5.x

Starting with BlueZ 5, pairing on Linux requires different code than
previous versions. While this code is already present, it currently
requires the user to manually define PSMOVE_BLUEZ5_SUPPORT in the build
in order to be used.

This fix implements automatic detection whether BlueZ version 5.x is used
in the build and handles the required define accordingly.