This adds the capability to compile got-portable on FreeBSD.

This commit modifies the GoT main branch to be able to compile it under linux.

This function is now being used by both 'got fetch' and 'got send' so its former name was misleading.

Both GOT_FETCH_PKTMAX and GOT_SEND_PKTMAX had the same value. Declare this value as GOT_PKT_MAX in got_lib_pkt.h instead.

These functions are used by 'got send' and 'got fetch' in order to open network connections to a server. Move them into new file lib/dial.c and declare relevant functions in got_dial.h and lib/got_lib_dial.h. No functional change.

On Linux, pipes returned from pipe(2) only work in one direction. This broke 'got clone' over ssh in the -portable version because got-fetch-pack assumes it can use its fetchfd for both reading and writing. I wrote a complicated diff to use two pipe(2) calls instead of one, but millert suggested a simpler solution: Use socketpair(2) instead of pipe(2). ok millert jrick tracey

Simplify dial_git() by formatting the initial Git protocol packet with dprintf, suggested by millert, and stop leaking an asprintf buffer. ok stsp

ok millert, naddy

ok naddy

ssizeof() macro idea courtesy of millert@ ok millert@

ok naddy@ stsp@

POSIX says the limits defined there are available from <limits.h>, which almost all affected source files already included anyway. ok millert stsp

ok stsp

ok stsp

it permits to .ssh/config to be honored same diff from stsp@

Both got-fetch-pack and got-index-pack now verify the pack file checksum. This means we can avoid reading the entire pack file in the main process just to verify its checksum and avoid a noticable stall between fetching and indexing on slow machines.