math.h change: add the _USE_MATH_DEFINES flag

By Patrick Spendrin <ps_ml@gmx.de>
  according to the msdn documentation
  http://msdn.microsoft.com/en-us/library/4hwaceh6.aspx _USE_MATH_DEFINES
  should give constants like M_PI etc.

  This patch adds it.

  regards,
  Patrick

git-svn-id: https://svn.code.sf.net/p/mingw-w64/code@6617 4407c894-4637-0410-b4f5-ada5f102cad1
hidpi.h: Added HidP_GetValueCaps and HidP_GetButtonCaps declarations.

git-svn-id: https://svn.code.sf.net/p/mingw-w64/code@6618 4407c894-4637-0410-b4f5-ada5f102cad1
Don't align _CONTEXT on ARM as the toolchain isn't ready for this yet

git-svn-id: https://svn.code.sf.net/p/mingw-w64/code@6619 4407c894-4637-0410-b4f5-ada5f102cad1
_chgsignl: Add ARM implementation

git-svn-id: https://svn.code.sf.net/p/mingw-w64/code@6620 4407c894-4637-0410-b4f5-ada5f102cad1