Turn on initial Ada support (mainly expression evaluation).

Turn on initial Ada support (mainly expression evaluation).

* Makefile.in (SFILES): Remove ada-tasks.c.
(HFILES_NO_SRCDIR): Add ada-lang.h.
(COMMON_OBS): Add ada-lang.o, ada-typeprint.o, ada-valprint.o.
(YYOBJ): Add ada-exp.o.
(rule .l.c): Generalize to not mention ada.
* symtab.c: Include ada-lang.h.
(symbol_natural_name, symbol_demangled_name)
(symbol_search_name): Add Ada case.