Refactor C-sources - common/constatns/debug/stack

 - move errors/debug code used only in src/*parser.c into this file
 - rename src/*common.* to src/*contants.*
 - exctract stack-related function to separate files src/*stack.*
Call try/catch/finally blocks in same-context as upper subrutine

to wantarray return same value inside try/catch/finally blocks as
outside.
Add test with redefined $SIG{__DIE__}
Extract "build optree functions" into separate file

 src/try-catch-optree.*
Refactor parsing catch-block return undef if none found

instead of empty array-reference.
Call last statement in try/catch/finally blocks in void context

 + add test for this change