Broadcast over vec(data) for row vectors

[jishnub]

On master

julia> A = BandedMatrix(0=>Float64[1:3000;]); v = rand(size(A,1));

julia> @btime $A .* $v';
  10.199 μs (5 allocations: 23.59 KiB)

This PR

julia> @btime $A .* $v';
  2.840 μs (7 allocations: 23.69 KiB)

Similar to #303, this also broadcasts over vec(data) if data is a row vector, to enforce the use of linear indexing.

[codecov]

Codecov Report

Base: 81.83% // Head: 81.81% // Decreases project coverage by -0.03% ⚠️

Coverage data is based on head (bb43f42) compared to base (e74f057).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #317      +/-   ##
==========================================
- Coverage   81.83%   81.81%   -0.03%     
==========================================
  Files          24       24              
  Lines        3320     3316       -4     
==========================================
- Hits         2717     2713       -4     
  Misses        603      603              

Impacted Files	Coverage Δ
src/generic/broadcast.jl	94.08% <100.00%> (-0.04%)	⬇️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[dlfivefifty]

I'm skeptical about these performance improvements that really should be in Base....

[jishnub]

I understand your concern, and I agree that these should be in Base. Hope that happens soon.