RequireMsgSym[_,_,Info] and more

[tribbloid]

This patch has the following 2 changes:

1. add Info as a validation option for RequireMsgSym

2. Warn and Info validation options for RequireMsgSym now also invoke scala compiler FontEnds logging.

The purpose of 2 is to allow warning and info logs to be identified by any build & code inspection systems, e.g. bloop language server in the following screenshot:

Unfortunately at this moment only INFO seems to be working. WARNING will be omitted by both scalac & bloop. It is probably caused by scala/bug#6910.

If you know the reason for this behaviour please let me know, I'll correct it

[codecov]

Codecov Report

Merging #186 (630137b) into master (f71754a) will decrease coverage by 1.00%.
The diff coverage is 20.00%.

@@            Coverage Diff             @@
##           master     #186      +/-   ##
==========================================
- Coverage   91.57%   90.56%   -1.01%     
==========================================
  Files          10       10              
  Lines         700      710      +10     
  Branches       11        9       -2     
==========================================
+ Hits          641      643       +2     
- Misses         59       67       +8     

Impacted Files	Coverage Δ
src/main/scala/singleton/ops/package.scala	100.00% <ø> (ø)
.../main/scala/singleton/ops/impl/GeneralMacros.scala	90.11% <20.00%> (-1.14%)	⬇️

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[tribbloid]

Sorry I don't know how to write unit test for this case, It appears that there is no coverage for Warn symbol as well, so I doubt if it could be tested

[soronpo]

Thanks for the PR. I'll only have time to review it next month.