Add initial .travis.yml file for Travis CI

+ Copied from https://github.com/dlintott/dynamips-fork
Ignore /build/* directory (commonly used for CMake builds)

[ci skip]
Create new README.md based on README for GitHub frontpage

+ Include travis build status

[ci skip]
Add common.h.
Move generic includes, types and macros from utils.h to common.h.
Minimize includes in sbox.c/h.
Minimize includes in crc.c/h.
CMake: build with -static and -static-libgcc in Cygwin
CMake:
 - allow empty DYNAMIPS_CODE and DYNAMIPS_ARCH, changed to the default value
 - DYNAMIPS_CODE is the option that controls what is built,
   not BUILD_DYNAMIPS_STABLE and BUILD_DYNAMIPS_UNSTABLE
 - DYNAMIPS_CODE can be "none"
Travis:
- install to test subdir
- try building the nojit architecture too
Merge branch 'master' of https://github.com/GNS3/dynamips
CMake: make sure we can compile with libelf, uuid, pcap
Travis: also try architecture x86
Travis: test doesn't work, try using another environment variable
Travis: split install by package and show more output to debug ARCH=i386
Tarvis: add install of cpp
Travis: disable x86 until I figure it out
CMake: test stripped library names when the detected lib fails
Travis: back to basics, install arch libraries and tell cmake where to look
Travis: ups, forgot to revert an incomplete change
Travis: add gcc-multilib and g++-multilib