Since doxygen 1.8.16, MSCGEN_PATH and PERL_PATH are obsolete:
MSCGEN_PATH:
873e0ccfbe
PERL_PATH:
6d1535c38f
I don't think that the notmuch builds ever depended on them in the
first place, and including them in the default config yields the
following two warnings:
```
doxygen ./doc/doxygen.cfg
warning: Tag 'PERL_PATH' at line 267 of file './doc/doxygen.cfg' has become obsolete.
To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u"
warning: Tag 'MSCGEN_PATH' at line 272 of file './doc/doxygen.cfg' has become obsolete.
To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u"
```
Remove them to avoid the warnings.
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
Many of the external links found in the notmuch source can be resolved
using https instead of http. This changeset addresses as many as i
could find, without touching the e-mail corpus or expected outputs
found in tests.
