Merge commit 'f51c84a' into gcc-4.8

Conflicts:
	source/machine-w64-mingw32/s-staall.adb

Modifications:
	source/machine-w64-mingw32/x86_64/s-unwmap.adb
	source/machine-w64-mingw32/x86_64/seh/s-unrase.adb
	source/machine-w64-mingw32/x86_64/seh/s-unwhan.adb
	source/machine-w64-mingw32/x86_64/seh/s-unwhan.ads
Write a project goal into readme.rst
Fix for the combination with 64bit Windows and SjLj
Improve examples/Makefile for speed up (and stop rm unexisting files)
Move Set_Exception_Message of the implementation unit System.Unwind.Raising to the spec
Unify 3-version s-unrase.adb into one
Merge commit '78fb34f' into gcc-4.8

Conflicts:
	source/machine-w64-mingw32/x86_64/seh/s-unrase.adb
	source/machine-w64-mingw32/x86_64/seh/s-unwhan.ads
	source/sjlj/s-unrase.adb
	source/sjlj/s-unwhan.ads
	source/zcx/s-unrase.adb
	source/zcx/s-unwhan.ads