2nd try at fix Issue 12989
Merge pull request #3739 from WalterBright/fix12989-2

2nd try at fix Issue 12989
fix Issue 13131 - [2.066-b3] dmd: glue.c:1492: unsigned int totym(Type*): Assertion `0' failed.
Do not call constructors from the glue layer (lib*)
Make construction of SignExtendedNumber explicit
Remove unnecessary line splicing in clone.c
Make color ddmd-friendly
Make narrowing cast explicit
Use explicit MOD type to avoid narrowing conversions from unsigned int
Merge pull request #3770 from yebblies/gluector

[DDMD] Do not call constructors from the glue layer (lib*)
Merge pull request #3772 from yebblies/linesplice

[DDMD] Remove unnecessary line splicing in clone.c
Merge pull request #3771 from yebblies/signext

[DDMD] Make construction of SignExtendedNumber explicit
Merge pull request #3769 from yebblies/DDMDMOD

[DDMD] Use explicit MOD type to avoid narrowing conversions from unsigned int
Merge pull request #3768 from yebblies/paintAsTypeddmd

[DDMD] Make narrowing cast explicit
Merge pull request #3767 from yebblies/ddmdcolor

[DDMD] Make color ddmd-friendly
Merge pull request #3764 from 9rnsr/fix13131

Issue 13131 - [2.066-b3] dmd: glue.c:1492: unsigned int totym(Type*): Assertion `0' failed.
Add manually ported frontend source files to version control
Add settings file and makefile targets to build ddmd
fix posix.mak ddmd rule
Add generated source to .gitignore