Since file-5.10 (end of 2011), libmagic identifies a C file in most
cases as "C source" instead of as "C program". Nano's magic strings
for some other files didn't match any more what file-5.32 currently
produces, either. So, they have been adjusted, new ones added, and
old ones deleted.
This fixes https://savannah.gnu.org/bugs/?52445.
Most of the keywords listed on the following URL are now highlighted:
http://php.net/manual/en/reserved.keywords.php
Also color single-quoted strings, and require that //-type comments
are preceded by whitespace or are alone on a line.
With-feedback-from: M <taur@mail.com>