Features: Record for Clang 3.4

Clang 3.4 supports all features currently known to CMake.
Features: Ensure that list exists to remove from.
Help: Fix whitespace in doc link.
cmTarget: Avoid copying container we don't need to copy.
file: Report system error on failure to open file
GNUInstallDirs: use the proper default for info and man paths on OpenBSD
OpenBSD: disable FIND_LIBRARY_USE_LIB64_PATHS

OpenBSD has no multilib paths.
Merge topic 'minor-cleanups'

d1035bd5 cmTarget: Avoid copying container we don't need to copy.
96eb97f8 Help: Fix whitespace in doc link.
0dffbb93 Features: Ensure that list exists to remove from.
Merge topic 'file-command-open-errors'

2c448dbf file: Report system error on failure to open file
Merge topic 'OpenBSD_no_multilib'

956b7190 OpenBSD: disable FIND_LIBRARY_USE_LIB64_PATHS
Merge topic 'GNUInstallDirs-OpenBSD'

d4fdd9c1 GNUInstallDirs: use the proper default for info and man paths on OpenBSD
Merge topic 'clang-features'

cda23319 Features: Record for Clang 3.4