[cleanup] fix indent style
Improve COMPILE_SEPARATELY to supply optional compiler switches when link .o files
Improve error propagation from function body semantic.
Change inNonRoot function to Dsymbol class member
fix Issue 11931 - Linkers "Symbol Undefined" again with dmd HEAD when -g specified

Also add test case for issue 7595.
Merge pull request #3107 from 9rnsr/fix11931

[REG2.065a] Issue 11931 - Linkers "Symbol Undefined" again with dmd HEAD when -g specified