Add generalized repmat function as repeat
Document repeat function

Extend ind2sub and sub2ind to accept a reusable array of indices
Expose rem1 and fld1, defined by analogy with mod1
Restore basic ind2sub definition
change string indexing to avoid invalid indexes in more cases, and
eliminate the thisind() function

For example, search("∀ x", "∀", 1) used to give 1:3, which doesn't
make much sense since the "3" is an artifact of the encoding and isn't
a valid index. Now it gives 1:1, or in general a:b where a is the index
of the first found character and b is the index of the last found character.
Let least squares solver return zeros instead of throwing an error when left hand side is zero
First draft of codespeedization of test/perf

* Change webhook notification URLs to julia.mit.edu (Linux) and criid.ee.washington.edu (OSX)
* Add `codespeed` target to test/perf/Makefile, which will run perfsuite and upload result to hardcoded codespeed installation location
  * Note that `make codespeed` will attempt to `Pkg.add()` the packages `JSON` and `Curl` if not already installed.
  * The sort subtests run a limited subset of 28 tests instead of almost 800
* Annotate all @time macro calls with an extra "Description" field, used to populate the codespeed database for the first time
* Until extra build-time information is provided, expect environment variables such as JULIA_FLAVOR, JULIA_BRANCH, and JULIA_COMMIT_DATE on the command line when `make codespeed` is invoked.
DLLEXPORTs for the profiler
Fix #3804, #3808
Also add rand(Float64, ...) and rand(Float32, ...)
Add additional like_pipe method for #3823
Add TTY(RawFD) for non-STDIO tty's

Also add the necessary c functions to extract the FD/Handle from a pipe object. These aren't used anywhere, but will be helpful for #3823
Added HeapSort

* Also minor updates to percolate_up, percolate_down, PriorityQueue
fix for 5975d2369d87aeae9d910ccaae82844eb951e915
fix crash in gc due to uninitialized memory in connect
inline the Union function
Partially revert "Add TTY(RawFD) for non-STDIO tty's"

This reverts the unrelated parts of commit
da00fa4d4867bfacc61b176f8a173393c251f283, which are broken on windows and
probably a generally bad idea on unix.
Merge pull request #3824 from kmsquire/heapsort

RFC: HeapSort
fix #3818
slight refactoring of show_backtrace to allow it to be used outside the REPL
rm redundant ptrint_t typedef
add licenses, for libraries bundled with windows dist, to LICENSE.md