Import vm, subject to the same treatment as vmc

[oleks]

• Make it build.
• Make 32-bit version build without warnings.
• Make 64-bit version build without warnings.
• Consider if src subdirectory is really necessary.
• Replace tabs with spaces.
• Strip trailing whitespace.
• Standardize header guards, and make sure they're always there
• Drop the old parameter syntax (parameter types specified outside the parentheses).
• Add -Wall to CFLAGS.
• Add -Wextra to CFLAGS.
• Add -pedantic to CFLAGS.
• Add -Werror to CFLAGS.
• Replace block-comments with line-comments