Add host layer support for pipes.

Windows does support pipes, but they do so in a slightly different way. Added a Host layer which abstracts the use of pipes into a new Pipe class that everyone can use.

Windows benefits include:
- Being able to interrupt running processes when IO is directly hooked up 
- being able to interrupt long running python scripts
- being able to interrupt anything based on ConnectionFileDescriptor



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@212220 91177308-0d34-0410-b5e6-96231b3b80d8
lldb - problem with some PTRACE_* constants in NativeProcessLinux.cpp file

See http://reviews.llvm.org/D4366 for details.

Change by Paul Paul Osmialowski

Today this is the only problem that I'm facing trying to cross-compile lldb for AArch64 using Linaro's toolchain.

PTRACE_GETREGS, PTRACE_SETREGS, PTRACE_GETFPREGS, PTRACE_SETFPREGS are not defined for AArch64
These things can be defined different ways for other architectures, e.g. for x86_64 Linux, asm/ptrace-abi.h defines them as preprocessor constants while sys/ptrace.h defines them in enum along with corresponding PT_* preprocessor constants
NativeProcessLinux.cpp includes sys/ptrace.h
To avoid accidental redefinition of enums with preprocessor constants, I'm proposing this patch which first checks for PT_* preprocessor constants then checks for PTRACE_* constants then when it still can not find them, it defines preprocessor constants.
Similar approach was already used for PTRACE_GETREGSET and PTRACE_SETREGSET constants; in this case however it was easier, since enum values in sys/ptrace.h and preprocessor constants shared all exactly the same names (e.g. there's no additional PT_GETREGSET name defined).


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@212225 91177308-0d34-0410-b5e6-96231b3b80d8