lang/rexx-regutil: several patches

• additional MASTER_SITE (there was only one)
• tidied Makefile considerably
• fixed failure to build under different PREFIX
• added DOC option
• added EXAMPLES option, and now can have examples (there were none before)
• eliminated numerous compilation warnings
• REMOVED pkg-plist (only two files in it)
• REMOVED pkg-message (now redundant)
• ADDED new patches in files/

PR: 209379
Submitted by: bob@eager.cx (maintainer)