added fctvprintf() - vprintf with output function

[usaygo]

Thanks for nice printf() implementation :)
The vprintf with output function may help integration where printf like function has already been declared.

[codecov-io]

Codecov Report

Merging #65 into master will decrease coverage by 0.82%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master      #65      +/-   ##
==========================================
- Coverage     100%   99.17%   -0.83%     
==========================================
  Files           1        1              
  Lines         359      362       +3     
==========================================
  Hits          359      359              
- Misses          0        3       +3

Impacted Files	Coverage Δ
printf.c	99.17% <0%> (-0.83%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 21eea6c...fdba0a0. Read the comment docs.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (master@21eea6c). Learn more about missing BASE report.
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
printf.c	0.00%	3 Missing ⚠️
❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff            @@
##             master      #65   +/-   ##
=========================================
  Coverage          ?   99.17%           
=========================================
  Files             ?        1           
  Lines             ?      362           
  Branches          ?        0           
=========================================
  Hits              ?      359           
  Misses            ?        3           
  Partials          ?        0           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.