Add .gitignore file

Improves quality of 'git status'.  Use 'git ls-files -o' to see all
untracked files.

Signed-off-by: Zachary T Welch <zwelch@codesourcery.com>

.gitignore

@@ -0,0 +1,52 @@
+*.la
+*.a
+*.o
+*.lo
+*~
+
+.libs/
+.deps/
+
+.dirstamp
+Makefile
+Makefile.in
+
+INSTALL
+aclocal.m4
+autom4te.cache/
+config.log
+config.status
+config/
+configure
+libtool
+
+doc/common.tex
+
+include/config.h
+include/config.h.in
+include/libunwind-common.h
+include/stamp-h1
+
+tests/[GL]test-bt
+tests/[GL]test-concurrent
+tests/[GL]test-dyn1
+tests/[GL]test-exc
+tests/[GL]test-init
+tests/[GL]test-resume-sig
+tests/[GL]perf-simple
+tests/Ltest-nomalloc
+tests/Lperf-simple
+tests/check-namespace.sh
+tests/forker
+tests/mapper
+tests/rs-race
+tests/test-async-sig
+tests/test-flush-cache
+tests/test-init-remote
+tests/test-mem
+tests/test-ptrace
+tests/test-setjmp
+tests/test-strerror
+tests/test-proc-info
+tests/test-ptrace-misc
+tests/test-varargs