Combine pkg-config caches
Fix escaping empty flags
Rewrite gr_linear_rep_movsdm with std::transform

Eliminate deprecated register.
Refactor gr_ubitmap012
Pack listbox better
Use range_for in light rendering
Rewrite scale_line to use std::fill

Eliminate inline byte-by-byte store.
Fix some -Wsign-compare warnings
Use pkg-config on Darwin if available