Disallow package names with dots.

They cannot be used as arguments (Perl thinks it's version check, but
version checks are pointless for oneliners), and Debian puts path
containing version depending directories (like 5.14.2) in Perl path.
Fix for errant SIGHUPs due to child fish shells messing with the term.
Fixes https://github.com/fish-shell/fish-shell/issues/1002
Clean up interactive session test
Fix formatting
add completions for source and document the move away from '.'

Closes: #310
use docdir from configure in setting __fish_help_dir
Closes #1065
set docdir in Xcode build
fixes part of #1070
Link with $CXXFLAGS; disable GCC-specific autoconf check (squash fixes).
update URL for nightly builds
Make type -a print all executables in PATH
clobber the prompt when it exceeds the screen width, not when it equals it

Closes #1069
Fix broken links in tutorial
Implement file autocompletion for git add and git checkout.

Fixes bpinto/oh-my-fish#59.
s/Procces/Process/. Fixes #1082.
Integrated new German translation provided by Benjamin Weis
improve diagnostics for socket connections to fishd
configure/Makefile: respect $LIBS, remove some egregarious lies

 - expunge LIBS_COMMON, it doesn't get used anywhere
 - don't reset LIBS to empty
 - move the gettext test as every binary depends on it
 - only include one set of libraries
Prefer standard library lzma module if available

Prefer the standard library lzma module if available.  This change prevents
using the backports-lzma when it is installed for a version of Python that
already has the lzma module in its standard library.