(cherry picked from commit 15d0f327)

(cherry picked from commit 8c63ea43)

(cherry picked from commit abbefd71)

Remove unnecessary "fmt/" prefix which should be maintained with additional include_directories() in each project. (#397)

(cherry picked from commit 1500f005)

(cherry picked from commit cee50b75)

(cherry picked from commit 9ec3bea2)

(cherry picked from commit 5f26b5da)

(cherry picked from commit 04335aea)

(cherry picked from commit a79c7b4e)

(cherry picked from commit 53f9e7f6)

(cherry picked from commit 2bf59a97)

(cherry picked from commit 12a6027b)

(cherry picked from commit a5d0adf3)

(cherry picked from commit 1a23f9c2)

(cherry picked from commit ed301089)

(cherry picked from commit 1dbc6bd1)

(cherry picked from commit c8c99736)

(cherry picked from commit c110c6ec)

(cherry picked from commit 1acfd07f)

(cherry picked from commit 903357c8)

(cherry picked from commit d7c4e1cb)

(cherry picked from commit 86316940)

(cherry picked from commit 0e6df7e5)

Building under a recent clang compiler causes the use of an extern
template for the BasicData struct. However, the only instantiation of
that structure in format.cc is only done if FMT_HEADER_ONLY is not
defined. This causes the build to fail in C++11 or C++14 mode.
Therefore, only declare the BasicData template as extern if
FMT_HEADER_ONLY is not defined.

(cherry picked from commit 75f862bf)

(cherry picked from commit 5c876088)

(cherry picked from commit 2e69e454)

(cherry picked from commit e0d6f630)

(cherry picked from commit a201c619)

(cherry picked from commit 4569b4db)

(cherry picked from commit c9bb5468)

(cherry picked from commit b26e76ef)

(cherry picked from commit c7739536)

(cherry picked from commit 18e3f165)

(cherry picked from commit 231c16df)

(cherry picked from commit e68836c1)

(cherry picked from commit dc1e36fa)

(cherry picked from commit 7bb1b508)