Mihaela Chirea - SAOC 2020 Milestone 2 Update 1 - Improving DMD as a Library

[Mihaela Chirea]

Hello!

Sorry for posting so late but here is the first update of 
Milestone 2 of #SAOC2020

The plans for this past week were to add the start locations to 
all the AST nodes that lack it. Here is what I have done so far:
- Removed TOK.arrow as I noticed it was unused [1]
- Added the start location to DebugCondition and VersionCondition 
[2]
- Started working on adding location to linkage symbols [3]

Next steps:
- Bring all DMD as a library additions hidden behind a version 
under DMDLIB (as this would be a fast change)
- Continue adding locations to the remaining AST nodes

The tasks I plan to do during this milestone can be found here [4]

[1] https://github.com/dlang/dmd/pull/11895
[2] https://github.com/dlang/dmd/pull/11907
[3] https://github.com/AsterMiha/dmd/tree/LinkageLoc
[4] 
https://forum.dlang.org/post/kfcxcjauafpcrmfuajam@forum.dlang.org