In UTF-8 locales, the ranges A-F and a-f include several accented
characters beyond "ABCDEF" and "abcdef", such as the Croat č and ć.
This fixes https://savannah.gnu.org/bugs/?61487.
Bug existed since the beginning of each of the syntaxes,
for the C syntax since version 1.3.6, commit 159bdfdc.
A backslash should not be allowed inside a quoted string unless
it is used to escape another character.
This fixes https://savannah.gnu.org/bugs/?61389.
Bug existed since each of these syntaxes was introduced.
(Awk and Fortran do not know include files with names between
angled brackets, so those regexes are dropped in the bargain.)
Quoted strings cannot start within another quoted string and end after
that other string has ended. Therefore single-quoted and double-quoted
strings should (as much as possible) be colorized by a single rule, so
that overlapping colorations are avoided.
(This also fixes a double typo in the PHP syntax (\. --> \\.) that has
been there since the PHP syntax was added in 2008, commit 90ee8ee4.)
This fixes https://savannah.gnu.org/bugs/?61387.
Bug existed since each of these syntaxes was introduced,
the oldest ones around 2006, a few others around 2015.
The one that got it right was the Lua syntax from 2011.
In many places a carriage return is not valid whitespace and should
thus not be colored as such. In some of these places a vertical tab
or form feed is maybe valid whitespace, but it would be ugly or even
wrong to color them because they are not part of the subsequent
comment or keyword.
This fixes https://savannah.gnu.org/bugs/?60456.
Also, remove the coloring of special single-quoted strings as they
get recolored by the subsequent general string-coloring command.
And remove the coloring of all-uppercase words, as other editors
do not color those either.
