Refactor travis build to use clang's sanitizers

- Valgrind configuration removed
- Fix errors reported by the undefined behavior sanitizer
- Travis will now run two build steps:
  - A normal build of a shared library for unit testing(in parallel with gcc)
  - A clang build with some sanitizers enabled for integration testing.

After these changes travis will run much faster, while providing valgrind-like
error detection.
refactored logic from init_users() into mch_get_usernames()
moved mch_get_user_name() and mch_get_uname() into os/users.c
removed get_user_name() and replaced calls with mch_get_user_name()
refactored part of expand_env_esc() into mch_get_user_directory()
Fix: Use an assert to make sure, an error message can be copied into buffer buf in mch_dirname().

The copied error message is NUL-terminated.
Remove remaining hangul-related code
add .vimrc and src/.ycm_extra_conf.py
Include <stdint.h> in types.h
Replace UINT32_T by uint32_t
Remove useless sizeof(uint32_t) == 4 test
Extract indent_c.c from misc1.c
Adapt include guards to the style guide
Use include paths relative to src/

As described in Google's style guide, the basis for Neovim's

> All of a project's header files should be listed as descendants of the
> project's source directory without use of UNIX directory shortcuts .
> (the current directory) or .. (the parent directory).

Add src as an include directory to facilitate this.
Revamp the build system.

This achieves several goals:

 * Less reliance on scripts so we have better portability to Windows
   (though we still have a ways to go for proper Windows support).
   Luajit, luarocks, moonscript, and busted are all installed via CMake
   now.
 * Trying to make use of pkg-config to get the correct libraries.  The
   latest libuv is still broken in this regard, but we'll at least be in
   a position to use it.
 * Allow the use of Ninja or make.  The former runs faster in many
   environments, and automatically makes use of parallel builds.

This also allows for system installed dependencies--though not through
the Makefile just yet--and adds support for FreeBSD.

This also make us build libuv and luajit as static libraries only, since
we're only concerned about having static libraries for our bundled
dependencies.
Deal with the missing dependencies for libuv.

Since libuv.pc is broken at the moment, try to determine libuv's
dependencies ourselves.  This ports most of the checks from libuv into
our CMake build, and fixes the build on other unix platforms.
Workaround the broken progress feedback in some versions of CMake.

Underneath the hood, CMake uses libcurl and libcurl has had a number of
issues regarding progress feedback.  In one sample run against Travis
CI, we ended up with nearly 3,000 lines of progress output for a single
download.

Unfortunately, CMake doesn't have the download and extract steps
separate, so we have some extra work that we have to do.  Much of the
content was taken from the ExternalProject.cmake and it's template for
generating the content of the download and extract CMake files.