Fix progress bar assertion
Add a configure option to disable assertions

Adds a --disable-assert configure option. We **highly recommend** the
use of this option by distro maintainers so as to ensure a smooth
experience with Wget. Sometimes an assertion may fail even though Wget
continues to work perfectly. In such scenarios, we do not wish for
client installations of Wget to crash. Hence, for a stable experience,
please use the --disable-assert configure flag.
Fix make syntax-check.
Scroll to last character of filename in progress
Fix mangled gitignore file
gnulib: Pull submodule forward
Update bootstrap script
Remove autogenerated file from sources

po/stamp-po is automatically generated / downloaded upon running make
and hence should not be a part of the checked out sources