portable: configure: split out dependencies Rather than assume all dependencies are required for all programs, split them out. This will make packaging easier, as well as splitting the code to use subprojects. Note that due to the use of config.h semantics, in most cases the got_compat.h header file is now at the top of the .c file it is included in, so that it can handle the system header inclusion properly.

portable: rework SHA detection Simply the SHA detection by not predicating on libcrypto, but instead checking individual header files.

portable: remove sha1.h; found portably Remove sha1.h as this is found portably across systems.

include sha2.h too where sha1.h is included In preparation for wide sha256 support; stsp@ agrees. Change done mechanically with find . -iname \*.[cy] -exec sam {} + X ,x/<sha1\.h>/i/\n#include <sha2.h>

avoid copying reused deltas to delta cache file; copy from pack file instead ok op@

let callers of got_pack_create() configure rate-limiting of progress reporting Needed by future gotd(8), where progress reports will be sent to a network socket, rather than a local terminal.

portable: fixup portably-included headers Remove certain headers which are included portably.

move privsep code from pack_create.c into new file pack_create_privsep.c Needed by future gotd(8). ok op@