3.5.0

This release of optional lite contains the following changes:

Additions:

• Add script tc-cl.bat (nonstd-lite-project issues 54).
• Add macro optional_static_assert() and compile-time checks on T.
• Add PlatformIO library manifest file library.json (replaces #64, thanks to @Nullfati).
• Add export() to CMakeLists.txt enabling importing targets. See nonstd-lite-project issues 50.

Changes:

• Enhance in-place construction (#66, thanks @@fekir).
• Change to use #if defined(_MSC_VER) to avoid -Wundef warning (#65, thanks @eepp).
• Change usage of =default with test structures to VS2015 for (#61).
• Handle lest test framework as system include to prevent warnings.

Fixes:

• Fix value_or() from changing stored value (issue #60, thanks @deadem, @mortenfyhn and @phprus).