Merge pull request #3627 from 9rnsr/fix12860

[REG2.065] Issue 12860 - typeid(_error_) symbols leaked to backend
Delete unconvertable comment
Move #defined constants outside class declaration
Make narrowing conversion explicit
Fix Issue 12873 - Valgrind unhandled instruction bytes 0x48 0xDB (redundant REX_W prefix on x87 load)
Fix Issue 10054 - x86_64 valgrind reports unrecognised instruction (DMD 2.062)
improve fix of issue 12860 for ddmd
Merge pull request #3631 from yebblies/classconstants

[DDMD] Move #defined constants outside class declaration
Merge pull request #3632 from yebblies/ucomment

[DDMD] Delete unconvertable comment
Merge pull request #3633 from yebblies/ctfenarrow

[DDMD] Make narrowing conversion explicit
Merge pull request #3636 from 9rnsr/fix12860

improve fix of issue 12860 for ddmd
Merge pull request #3634 from yebblies/issue12873

Issue 12873 - Valgrind unhandled instruction bytes 0x48 0xDB (redundant REX_W prefix on x87 load)
Merge pull request #3635 from yebblies/issue10054

Issue 10054 - x86_64 valgrind reports unrecognised instruction (DMD 2.062)