cmd/compile: include non-decomposed vars for -dwarflocationlists
When enhanced DWARF location list generation is enabled (via internal
option -dwarflocationlists), variable entries were missing for "large"
(non-decomposable) locals and formals. From the debugging perspective,
this makes it appear that the variable doesn't exist, which is
probably not what we want. This change insures that a formal/local DIE
is created for these vars (with correct type, line, etc) but with a
conservative ("no info") location.