GCC may have support for __has_feature but doesn't support __has_builtin

So perform these checks separately
Merge pull request #46 from amorozov/bug/45

GCC may have support for __has_feature but doesn't support __has_builtin
Unindent
Fix grow size during Array<>::append

When the resulting array must grow during append, one must make sure
that the new elements _plus_ the current elements fit the new array
size.
Merge pull request #47 from Jopie64/master

Fix grow size during Array<>::append
Add a test case for https://github.com/cppformat/cppformat/pull/47
Implement printf specifications.
Merge branch 'master' of github.com:cppformat/cppformat
Implement dynamic width in printf.
Clean
Parse printf format specs.
Implement integer precision.
Implement precision + fill.
PrepareFilledBuffer -> PrepareBufferForInt
Fix handling of octal prefix.
Use stock version of breathe as it provides control over member visibility now.
Make precision and alignment work together.
Predefine _WIN32 for Windows-only parts of API.
Use precision from FormatSpec.
Add Usage section.