- Copy stable/10@296371 to releng/10.3 in preparation for 10.3-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.3.
- Update default pkg(8) configuration to use the quarterly branch.

Approved by: re (implicit)

MFC r271651, r271719, r272138, r272457, r272845, r275476, r275518, r275614,
r275819, r276176, r278154, r278160, r278339, r279127, r279240, r279491,
r279493, r279856, r283032, r284423, r284426, r284427, r284428

Merge changes to libm from the past 9 months. This includes improvements
to the Bessel functions and adds the C99 function lgammal.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Use cpack() and the gcc extension __imag__ to implement cimag() and
conj() instead of using expressions like z * I. The latter is bad for
several reasons:

1. It is implemented using arithmetic, which is unnecessary, and can
generate floating point exceptions, contrary to the requirements on
these functions.

2. gcc implements complex multiplication using a formula that breaks
down for infinities, e.g., it gives INFINITY * I == nan + inf I.

Add implementations for cimag{,f,l}, creal{,f,l} and conj{,f,l}. They are
needed for cases where GCC's builtin functions cannot be used and for
compilers that don't know about them.

Approved by: das (mentor)