Since we switched from autotools to Meson in commit
94592c14, we don't need to include
`config.h` early to properly enable large file support.  Meson passes
the required macros on the compiler command line instead of defining
them in `config.h`.

This means we can include `config.h` at any time, whenever we want to
check its macros, and there are no ordering constraints.

Only _WIN32 is defined by the compiler, and WIN32 is not standardized
and may be missing.

Closes #169

This eliminates some overhead, because the compiler doesn't need to
consider these functions throwing.

There is not much use in GLib: on Windows, we have a native API for
string collation, and the rest uses either libicu or the standard C
library calls.

New in clang 3.6.

Again, POSIX says strcasecmp is not in string.h.

Turns out ucol_getSortKey() does not what I thought it does.

Fixes the broken "search" command.

Fixes crash after database update.

Fixes initialization failure.