Added missing curly brackets and fixed compiler warnings.
Disable SSL when compiling for AmigaOS for now.
Compile regexp dependency when AMIGA is defined.

Before it was compiled when CMake was actually run on AmigaOS.
Add -fPIC only if BUILD_SHARED_LIBS is ON
Ignore build-amiga
Sane refresh logic

All the ODB backends have a specific refresh interface. When reading an
object, first we attempt every single backend: if the read fails, then
we refresh all the backends and retry the read one more time to see if
the object has appeared.
dat errorcode
odb: Refresh on `exists` query too
Merge pull request #1218 from sba1/amiga.2

Libgit2 for AmigaOS4
Merge pull request #1182 from libgit2/odb-file-refresh

Sane refresh logic for #1180