Add FileDescriptor class

A simple class to wrap a file descriptor so it can
be opened on construction and closed on destruction.

Change-Id: I16d481fdc91e99720acd9cabff3a3a4690d8a573
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/Makefile.am b/Makefile.am
index ef50fa1..cc2374a 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -6,6 +6,7 @@
 openpower_proc_control_SOURCES = \
 	proc_control.cpp \
 	p9_procedures.cpp \
+	filedescriptor.cpp \
 	targeting.cpp
 
 openpower_proc_control_LDFLAGS = $(PHOSPHOR_LOGGING_LIBS) -lstdc++fs