main.c: Misc. improvements

- Constify parameters and reduce char_u usage
- Modernize function signatures
- Modernize function comment blocks, rewriting if needed
- Factor out mainerr_arg_missing(); all the other ME_* macros lack
  such a wrapper function.

main_errors[]
  - Remove unneeded parentheses
  - Remove an unused error string and its respective macro

mainerr()
  - Don't print version when called. mainerr() only handles errors
    related to command line arguments, so the version isn't much help at
    all.
  - Changed 'vim' instance to 'nvim'

Misc.
  - Remove duplicate include
  - Replace unneeded 'inttypes.h' include with 'stdint.h'
  - Remove stray comments
  - Remove excessive newlines

0 files changed, 0 insertions, 0 deletions