Remove 'textauto' option

For the same reason we removed 'textmode'.
Remove "h" flag of 'highlight' option

HLF_H is an obsolete flag and got replaced by HLF_E.
Add the -Wconversion flag for some files.

This is to provide some infrastructure to help with issue #567 (Enable
-Wconversion file by file).
fix -Wconversion warnings for rstream

I'm not sure whether to go for signed or unsigned types for the offsets, but
without a doubt size_t is a better alternative than uint32_t. Added casts
after checking bounds before and after calling external libraries (in this
case libuv).
Remove dead code in clint.py
Allow USERNAME to be specified on the command line.

There are some systems that have usernames of the form DOMAIN\username,
which causes an invalid escape character to be inserted.  I was going to
add some escaping, but decided it would be best to just outright set the
value, since I don't want the DOMAIN portion in there anyways.
Remove proto as an include directory.

The proto directory was removed in 0ef90c13b72b74928bfb3c183c7a5bd7240b51ad.
Remove sizeof(int) < 4 related code
cleanup os_unixx.h
inline the rest of os_unixx.h into os_unix.c
Broken build on 32 bit: Fix -Wshorten-64-to-32.

Problem:

[ 48%] Building C object src/CMakeFiles/nvim.dir/os/mem.c.o
/Users/eliseo/projects/os/neovim/src/os/mem.c:9:32: error: implicit
conversion loses integer
      precision: 'uint64_t' (aka 'unsigned long long') to 'long_u' (aka
      'unsigned long')
            [-Werror,-Wshorten-64-to-32]
              return uv_get_total_memory() >> 10;
                ~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~^~~~~

Solution:

Avoid conversion. Make function return proper uint64_t.
Make users of the function accomodate the value if too big for them.
Broken build on 32 bit: Fix -Wtautological-constant-out-of-range-compare.

Problem:

[ 51%] Building C object src/CMakeFiles/nvim.dir/os/rstream.c.o
/Users/eliseo/projects/os/neovim/src/os/rstream.c:237:24: error: comparison of constant
      9223372036854775807 with expression of type 'size_t' (aka 'unsigned long') is always true
      [-Werror,-Wtautological-constant-out-of-range-compare]
  assert(rstream->fpos <= INT64_MAX);
         ~~~~~~~~~~~~~ ^  ~~~~~~~~~
/usr/include/assert.h:93:25: note: expanded from macro 'assert'
    (__builtin_expect(!(e), 0) ? __assert_rtn(__func__, __FILE__, __LINE__, #e) : (void)0)
                        ^

Solution:

Assertion temporarily disabled.
TODO: Review types so that assertion can be used.
Use libtinfo as a fallback for curses

This will be done before running the FindCurses cmake module
Configure travis to perform a 32-bit build

- Build targeting 32-bit with travis
- Code in `before_install`/`after_success` was moved to travis.sh since it
  provides greater flexibility for detecting the build matrix environment. This
  improves the build speed since we now install only what's necessary.
- Now clint has a dedicated travis worker
Fix clint.sh wrapper script and broken files

- Fixed clint.sh, it no longer ignores errors in individual files.
- Fixed two files that weren't passing the clint test
Use portable format specifiers: Case %lld - plain - sprintf.

Fix uses of plain "%lld" within sprintf():
- Replace "%lld" with "%" PRId64.
- Cast corresponding argument to (int64_t).
Use portable format specifiers: Case %lld - localized - sprintf.

Fix uses of localized "%lld" within sprintf():
- Replace _("%lld") with _("%" PRId64).
- Cast corresponding argument to (int64_t).
- In *.po files, replace "%lld" with "%<PRId64>".
Use portable format specifiers: Remove branching with LONG_LONG_OFF_T.

After previous commits, branching code by using macro LONG_LONG_OFF_T
becomes unneccesary. Remove it.
Use portable format specifiers: Case %ld - plain - sprintf.

Fix uses of plain "%ld" within sprintf():
- Replace "%ld" with "%" PRId64.
- Cast corresponding argument to (int64_t).
Use portable format specifiers: Case %ld - localized - sprintf.

Fix uses of localized "%ld" within sprintf():
- Replace "%ld" with "%" PRId64.
- Cast corresponding argument to (int64_t).