Removed unnecessary PATHS from cmake modules

- DEPS_INSTALL_DIR is already set into CMAKE_PREFIX_PATH in
  the main CMakeLists.txt
Merge #910 'Remove unnecessary PATHS from cmake modules'
FIX -Wconversion warnings for src/nvim/cursor_shape.c
add -Wconversion flag to src/nvim/cursor_shape.c
FIX -Wconversion warnings on src/nvim/os/channel.c
add -Wconversion flag for src/nvim/os/channel.c
remove duplicated map.c from src/nvim/CMakeLists.txt
TRIVIAL: fix trailing blanks in src/nvim/eval.c
FIX -Wconversion warnings in src/nvim/os/fs.c
add -Wconversion flag for src/nvim/os/fs.c
sort files in alphabetical order, for better reading
FIX -Wconversion warnings for src/nvim/os/input.c
add -Wconversion flag for src/nvim/os/input.c