Avoid C99 comments, use old-style C comments instead.

Avoid C99 comments, use old-style C comments instead.

This doesn't make the code uglier or harder to read, yet it makes the
code more portable.  This also simplifies checking for other potential
incompatibilities.  "gcc -std=c89 -pedantic" can flag many incompatible
constructs as warnings, but C99 comments will cause it to emit an error.

Signed-off-by: Pavel Roskin <redacted>
Signed-off-by: Junio C Hamano <redacted>