grc: no tooltips for old GTK versions
Fixed inconsistent spacing in perror output
fixed UHD manual URLs
Merge remote-tracking branch 'mmueller/runtime_fix_spacing_in_perror' into maint
Merge remote-tracking branch 'mmueller/gr_uhd_fix_URLs' into maint
Merge remote-tracking branch 'gnuradio-wg-grc/maint_grcwg' into maint