Fix crash loading TaskDialogIndirect with wrong calling convention.

While changing from `winapi::proc_address` to `winapi::load_function` (a05f6597) we lost the calling convention specifier for `TaskDialogIndirect`.  This caused a crash on 32-bit builds (64-bit has a single calling convention).

This commit replaces the specifier and updates to a version of winapi whose `load_function` is able to handle the calling convention specifier.

Fixes #267.
Updated Hebrew translation from Transifex.
Bump version number to 0.8.1 for release.
Update to latest OpenSSL (1.0.0l).
Updated NEWS for 0.8.1.
Merge branch 'release/0.8.1' into develop