Fix MSVC build in preprocessor conformance mode

[chfast]

We need to split "" and _u tokens in the DEFINE_ALIAS_AND_LITERAL macro to make it conformant with the C11 preprocessor.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.94%. Comparing base (72ae825) to head (beddb23).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #327   +/-   ##
=======================================
  Coverage   99.94%   99.94%           
=======================================
  Files          10       10           
  Lines        1811     1829   +18     
=======================================
+ Hits         1810     1828   +18     
  Misses          1        1           

Flag	Coverage Δ
32bit	99.94% <ø> (ø)
gcc	99.39% <ø> (?)

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Files with missing lines	Coverage Δ
include/intx/intx.hpp	99.85% <ø> (+<0.01%)	⬆️

... and 1 file with indirect coverage changes