2019-12 Update for AMSS3 (GSJ Open-file Report no.648)

Programs 'exdeq1','exdeq2','exdeq3','exdeq4', 'plmvarc', and 'genroff'
   were slightly modified, so as to improve the operationg condition.

Programs 'plmap', 'plmapc', 'plmapcl', 'plmapcs', 'plmapg', 'plmapl',
         'plmaps', 'shade', 'xplmap', 'xplmap', 'xplmapcs', 'pltrk',
         'plamag', 'plamagc', and 'plmvarc'
   were modified, so as to improve the automatic selection of ScaleBar
   drawimg size.

Programs 'ameq', 'ameqc', 'ameqs', 'ameqsc'
   were modified, so as to fix a bug.