coalesce all seq builtins into SeqFunctions
add fast paths for seq and seq.default
refactor and expand seq unit tests

Merge pull request #601 in G/fastr from ~LUKAS.STADLER_ORACLE.COM/fastr:bugfix/internal_rework_cleanup to master

* commit 'e26cb110':
  cleanups for “.Internal rework” changes

* commit 'd69524f7':
  minor clarifications in loop nodes

Merge pull request #598 in G/fastr from ~LUKAS.STADLER_ORACLE.COM/fastr:feature/special_attrs to master

* commit '89d1fb41':
  make SpecialAttributesFunctions more generic, use efficient isMatrix/isArray in more places

Merge pull request #596 in G/fastr from ~LUKAS.STADLER_ORACLE.COM/fastr:bugfix/shape_checked_attr_access to master

* commit 'd58971d4':
  pass shape to Location.get

* commit '6ec2c292':
  final, formatting, unused code
  organize imports

Merge pull request #594 in G/fastr from ~STEPAN.SINDELAR_ORACLE.COM/fastr:feature/all-distr to master

* commit '5569b051':
  Stats: port {q/p}tukey functions
  Stats: port non-central t distribution (externals: {p/q/d}nt)
  Stats: port signrank distribution functions

Merge pull request #588 in G/fastr from ~LUKAS.STADLER_ORACLE.COM/fastr:feature/internals_rework to master

* commit '564543fb':
  imports, static, and various other cleanups
  small cleanups
  fix copyright years
  make “isatty” INTERNAL
  enable passing test
  additional profile in FilterNode
  use RTypes for fast paths, additional type profile in SetDiffFastPath
  additional profiles in vector extract nodes
  use voidExecute in loops
  fix “options” to always set visibility
  move .Internal handling to AST creation, remove ForcePromiseNode, keep RSyntaxElement instead of RSyntaxNode in RCaller

move .Internal handling to AST creation, remove ForcePromiseNode, keep RSyntaxElement instead of RSyntaxNode in RCaller

Merge pull request #581 in G/fastr from ~LUKAS.STADLER_ORACLE.COM/fastr:feature/rcallnode_notification to master

* commit 'a8bef4f3':
  use GetCallerFrameNode in EnvFunctions
  notify RCallNodes in FrameFunctions
  change RCallNode to use assumptions to interact with GetCallerFrameNode

* commit '3f831635':
  rffi: fix thread safety related to recent change to use Nodes

* commit '7b62265d':
  one more options test
  fix copyright year
  generated expected output messages
  "editor" option can be also NULL or a function

* commit 'ab8ca7b6':
  fix copyright year
  generated expected output messages
  unify the crc algorithm in c.o.t.r.library.utils.Crc64 and c.o.t.r.nodes.builtin.base.CRC64

Merge pull request #590 in G/fastr from ~STEPAN.SINDELAR_ORACLE.COM/fastr:feature/nmath-refactoring-wilcox to master

* commit '49e5ba8c':
  Stats vs nmath structure refactoring + wilcox externals

- code corresponding to 'nmath' in GnuR moved to new package:
com.oracle.truffle.r.runtime.nmath
- it turns that Wilcox uses Choose, which is a builtin node, the original
structure did not allow code reuse in such cases
- implement wilcox externals {d/p/q}wilcox and wilcox_free + improved choose