#12853 introduced a regression, breaking nim js for program that import std/strtabs

Example

# main.nim: import std/strtabs

Current Output

nim js main.nim

strtabs.nim(327, 39) Error: invalid pragma: since: (1, 1) 

Expected Output

works

Possible Solution

• move since to system`; yes it adds 1 more thing to system, but since it affects exposing APIs, it belongs there, and also it really doesn't belong in inclrtl:

# Pragmas for RTL generation. Has to be an include, because user-defined # pragmas cannot be exported. 

and it can't be in a module that's imported because of current limitation (pragmas cannot be exported), so would require an include, which has known issues.

• in the future we can lift limitation (pragmas cannot be exported) to improve this a bit

Additional Information

D20191230T174936

• regression introduced in add a StringTable.clear that requires no mode specification #12853