Allows 'got commit' to use a ".diff" suffix for temporary diff files. ok op@

Needed by future gotd(8), where progress reports will be sent to a network socket, rather than a local terminal.

Future gotd(8) needs to run got_pack_create() in a chroot environment, so we can no longer open new temporary files inside got_pack_create(). ok op@

The old code required a seekable output file. This conflicts with requirements of future gotd(8), which will write pack file data to network sockets. ok op@

This can't happen in practice, but llvm's scan-build doesn't know this. OK stsp

Now that the handling of including sys/queue.h is better, there's no need to remove those lines from the source. Copy the location of those original sys/queue.h lines from upstream at the same line number, so as to avoid any conflicts in the future.

Saves us from doing a malloc/free call for every item on the list. ok op@

imsg_clear frees and closes resources allocated as part of enqueueing imsgs so it's a no-op after reads. discussed with and ok stsp@

tested by thomas, naddy, and myself

Suggested by naddy some time ago. ok tracey

suggested by millert ok thomas_adam

suggested by millert ok thomas_adam

sys/{tree,queue}.h are looked up via configure, and therefore are included via that mechanism.

Update portable to support changes for bloom, etc.

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

Add gotadmin to configure.ac, etc., so it can be built and installed. OK thomas.adam

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

Known to work against git-daemon and github Git server implementations. Tests by abieber, naddy, jrick, and myself. Man page additions reviewed by Lucas.