Add missing prereq.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13618 a5019735-40e9-0310-863c-91ae7b9d1cf9
Adjust CFLAGS and CXXFLAGS for compilation with clang. The current
setting suppresses almost all warnings originating in source code
constructs. It does ot yet suppress warnings from unrecognised command
line flags as they may be the reason for regression test failures
which have not yet been investigated.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13619 a5019735-40e9-0310-863c-91ae7b9d1cf9
Disable drd/tests/std_thread.cpp for clang.
clang 3.3 produces an error message for /usr/include/c++/4.6/chrono
which happens to get included somewhere inside <thread>.
This happens with C++ headers from:
gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3. 


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13620 a5019735-40e9-0310-863c-91ae7b9d1cf9