Added the start of platform configuration designed for internal LLDB use.

Internal use means for compiling the LLDB debug engine and plug-ins, but it
should never make it into the public API.

Since we don't currently have a configuration script that detects avaiable
functionality in the LLDB build system, we are hard coding #define values
in the host specific "Config.h" files. 

#define values in these Config.h header files should set the value to zero or
one:

#define LLDB_CONFIG_TERMIOS_SUPPORTED 1

#define LLDB_CONFIG_OTHER 0

Then any code in the LLDB engine should check the availability using:

#if LLDB_CONFIG_TERMIOS_SUPPORTED
....
#endif

Eventually the contents of the host specific Config.h files will be auto
generated, but for now they will be hard coded. Any LLDB_CONFIG_XXXX items
that are added should be added to all Config.h files and set to either zero
or one.

llvm-svn: 124892