crypt32: Introduce a space checking helper for functions that don't allocate memory and use it where appropriate.

dbghelp & imagehlp: Fix the PSYM_ENUMSYMBOLS_CALLBACK() and PSYM_ENUMERATESYMBOLS_CALLBACK() prototypes.

Tweak the actual callbacks to better match the prototypes.

widl: None of the non-fixed arrays have fixed sizes, so don't set the alignment to anything and return a size of 0 from get_required_buffer_size_type.