Tweak to avoid a trailing space.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13627 a5019735-40e9-0310-863c-91ae7b9d1cf9
Add a specific configury check to test compilability of the
<thread> C++ header file by the selected compiler.
Suggested by Bart Van Assche.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13628 a5019735-40e9-0310-863c-91ae7b9d1cf9