API fix and missing headers.

Host.cpp was missing Error.h and the implementation of
LaunchProcess. Once againg I have added a "fake" implementation
waiting for a real one.

Fixed the call GetAddressRange to reflect the new interface in
DynamicLoaderLinuxDYLD.cpp.

Added string.h to ARM_DWARF_Registers.cpp that is needed for ::memset.

Signed-off-by: Johnny Chen <johnny.chen@apple.com>
llvm-svn: 131695