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).