Improve style/consistency among the ports I maintain

• Convert to COPYTREE_SHARE
• Drop unnecessary MKDIR before COPYTREE_SHARE
• Drop bsd.port.options.mk if only DOCS requires it without dependencies
• Use separate backup if several REINPLACE_CMD against the same file
• audio/alsa-utils: convert to LIBS

Differential Revision: https://reviews.freebsd.org/D1851
Approved by: bapt (mentor)