Add .gitignore files

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

.gitignore

@@ -0,0 +1,21 @@
+*.a
+*.o
+*.pb.cc
+*.pb.h
+.deps
+Makefile
+Makefile.in
+
+/INSTALL
+/aclocal.m4
+/autom4te.cache
+/config.h
+/config.h.in
+/config.log
+/config.status
+/configure
+/depcomp
+/install-sh
+/missing
+/mosh-*.tar.gz
+/stamp-h1

src/examples/.gitignore

@@ -0,0 +1,5 @@
+/decrypt
+/encrypt
+/ntester
+/parse
+/termemu

src/frontend/.gitignore

@@ -0,0 +1,2 @@
+/mosh-client
+/mosh-server