syntaxes: use one regex for coloring quoted strings, to avoid overlap

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.

syntax/autoconf.nanorc

@@ -17,7 +17,7 @@ color cyan "\<[[:upper:]_[:digit:]]+\>"
 color red "\<[-_.0-9]+\>"
 
 # Strings:
-color red ""[^"]*""  "'[^']*'"
+color red ""[^"]*"|'[^']*'"
 
 # Backticks:
 color green "`[^`]*`"

syntax/extra/gentoo.nanorc

@@ -41,7 +41,7 @@ color blue "\<(awk|cat|cd|chmod|chown|cp|echo|env|find|e?grep|ln|make|mkdir|mv|p
 ## Comments (doesn't work that well):
 color yellow "(^|[[:space:]])#.*"
 ## Strings (doesn't work that well):
-color brightyellow ""(\\.|[^\"])*"" "'(\\.|[^'])*'"
+color brightyellow ""(\\.|[^\"])*"|'(\\.|[^'])*'"
 ## Trailing space is bad!
 color ,green "[[:space:]]+$"
 ## Mixed whitespace is also bad.

syntax/go.nanorc

@@ -34,8 +34,7 @@ color red "\<[0-9]+i\>"
 
 # Strings and characters; slightly fuzzy.
 color red "\<(true|false|nil|iota|_)\>"
-color red "'(\\.|[^'])+'"
+color red ""(\\.|[^"])*"|'(\\.|[^'])+'"
-color red ""(\\.|[^"])*""
 color red start=""(\\.|[^"])*\\[[:blank:]]*$" end="^(\\.|[^"])*""
 
 # Comments.

syntax/javascript.nanorc

@@ -17,7 +17,7 @@ color cyan "\<([0-9]+|0x[0-9A-Fa-f]+)\>"
 color cyan "\<(true|false|null|undefined)\>"
 
 # Strings.
-color brightmagenta ""(\\.|[^"])*"" "'(\\.|[^'])*'" "`(\\.|[^`])*`"
+color brightmagenta ""(\\.|[^"])*"|'(\\.|[^'])*'|`(\\.|[^`])*`"
 # Comments.
 color brightblue "(^|[[:blank:]])//.*"
 color brightblue start="/\*" end="\*/"

syntax/nftables.nanorc

@@ -26,7 +26,7 @@ color cyan "(^|[[:blank:]])#.*"
 color ,green "[[:space:]]+$"
 
 # Strings and others
-color yellow ""(\\.|[^"])*"" "'(\\.|[^'])*'"
+color yellow ""(\\.|[^"])*"|'(\\.|[^'])*'"
 color green "[][{}():;|`$<>!=&\]"
 
 # Basic variable names

syntax/php.nanorc

@@ -25,7 +25,7 @@ color brightcyan "\<(and|or|xor)\>"
 color magenta "\<(break|continue|goto|return)\>"
 
 # Strings.
-color brightyellow ""(\.|[^"])*"" "'(\.|[^'])*'"
+color brightyellow ""(\\.|[^"])*"|'(\\.|[^'])*'"
 
 # Comments.
 color brightblue "(^|[[:blank:]]+)//.*"

syntax/python.nanorc

@@ -24,8 +24,7 @@ color brightcyan "\<(exec|print)([[:blank:]]|$)"
 color brightmagenta "\<(False|None|True)\>"
 
 # Mono-quoted strings.
-color brightgreen "'([^'\]|\\.)*'|'''"
+color brightgreen "'([^'\]|\\.)*'|"([^"\]|\\.)*"|'''|""""
-color brightgreen ""([^"\]|\\.)*"|""""
 color normal "'''|""""
 # Comments.
 color brightred "(^|[[:blank:]])#.*"

syntax/sh.nanorc

@@ -33,7 +33,7 @@ color brightred "\$\{[#!]?([-@*#?$!]|[0-9]+|[[:alpha:]_][[:alnum:]_]*)(\[([[:bla
 color cyan "(^|[[:blank:]])#.*"
 
 # Strings.
-color brightyellow ""(\\.|[^"])*"" "'(\\.|[^'])*'"
+color brightyellow ""(\\.|[^"])*"|'(\\.|[^'])*'"
 
 # Trailing whitespace.
 color ,green "[[:space:]]+$"

syntax/tcl.nanorc

@@ -17,7 +17,7 @@ color green "\<(alarm|auto_load_pkg|bsearch|catclose|catgets|catopen|ccollate|cc
 # Syntax:
 color brightblue "\<proc[[:blank:]]|\{|\}"
 color green "\(|\)|\;|`|\\|\$|<|>|!|=|&|\|"
-color brightyellow ""(\\.|[^"])*"" "'(\\.|[^'])*'"
+color brightyellow ""(\\.|[^"])*"|'(\\.|[^'])*'"
 color brightred "\$\{?[0-9A-Za-z_!@#$*?-]+\}?"
 
 # Trailing whitespace: