cleanup: use ' ' instead of 32 to clarify meaning

The use of the literal ' ' for space makes the meaning much clearer
than the use of the ASCII code.

In the compiled code there is no difference.
scripts/add-hardware: avoid expansions for $BUTTONS_INPUT_SUPPORT

The quotes and backticks in the template for $BUTTONS_INPUT_SUPPORT
make bash & dash fail, as both try to expand the text.

Make sure the contents of this template does not get expanded by
surrounding the delimiter with quotes.
This keeps bash & dash happy.
scripts/add-hardware: add vi as fallback editor

Use the standard editor of UNIX "vi" as an additional fallback to allow
editing the freshly generated pinning file for those folks that do
not have $EDITOR set nor have nano installed.
compile_magic: make httpd_mimetype_plain[] const

Unbreak compilation by declaring httpd_mimetype_plain[] const.
DHCP: support reuesting NTP server

Request the NTP server from the DHCP server (option 42) and initialize
NTP if NTP_SUPPORT is configured.

This makes DHCP feature-equivalent to BOOTP.
Merge pull request #184 from marschap/misc-fixes

Misc fixes for master