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
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).
Use portable format specifiers: Case %ld - plain - fprintf.

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

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

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

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

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

Fix uses of localized "%ld" within vim_snprintf_add():
- Replace "%ld" with "%" PRId64.
- Cast corresponding argument to (int64_t).
Use portable format specifiers: Adapt EMSGN/emsgn to use (int64_t).
Use portable format specifiers: Case %ld - plain - EMSGN.

Fix uses of plain "%ld" within EMSGN():
- Replace "%ld" with "%" PRId64.
- No argument cast needed. EMSGN() will take care of that.
Use portable format specifiers: Case %ld - localized - EMSGN.

Fix uses of localized "%ld" within EMSGN():
- Replace "%ld" with "%" PRId64.
- No argument cast needed. EMSGN() will take care of that.
Use portable format specifiers: Case %ld - localized - N_.

Fix uses of plain "%ld" within N_():
- Replace "%ld" with "%" PRId64.