Bug 1799982 - Remove uses of inline flags from XPIDL regexps. r=xpcom-reviewers,kmag

Apparently the use of these is being turned into an error in Python 3.11.
Fortunately, our uses appears to be rather trivial.

For t_multilinecomment and t_LCDATA, I dropped the (?s) flag and just
replaced the one use of . with (\n|.). (?s) means DOTALL, which means
that dot includes any character, including a newline. Otherwise it means
dot includes any character except a newline.

I took the new t_singlelinecomment from IPDL's parser.py, so I assume
it is reasonable enough. t_multilinecomment is also now the same as
in IPDL.

Differential Revision: https://phabricator.services.mozilla.com/D161738

diff --git xpcom/idl-parser/xpidl/xpidl.py xpcom/idl-parser/xpidl/xpidl.py
--- xpcom/idl-parser/xpidl/xpidl.py
+++ xpcom/idl-parser/xpidl/xpidl.py
@@ -1634,36 +1634,36 @@ class IDLParser(object):
     t_LSHIFT = r"<<"
     t_RSHIFT = r">>"
 
     literals = '"(){}[]<>,;:=|+-*'
 
     t_ignore = " \t"
 
     def t_multilinecomment(self, t):
-        r"/\*(?s).*?\*/"
+        r"/\*(\n|.)*?\*/"
         t.lexer.lineno += t.value.count("\n")
         if t.value.startswith("/**"):
             self._doccomments.append(t.value)
 
     def t_singlelinecomment(self, t):
-        r"(?m)//.*?$"
+        r"//[^\n]*"
 
     def t_IID(self, t):
         return t
 
     t_IID.__doc__ = r"%(c)s{8}-%(c)s{4}-%(c)s{4}-%(c)s{4}-%(c)s{12}" % {"c": hexchar}
 
     def t_IDENTIFIER(self, t):
         r"(unsigned\ long\ long|unsigned\ short|unsigned\ long|long\ long)(?!_?[A-Za-z][A-Za-z_0-9])|_?[A-Za-z][A-Za-z_0-9]*"  # NOQA: E501
         t.type = self.keywords.get(t.value, "IDENTIFIER")
         return t
 
     def t_LCDATA(self, t):
-        r"(?s)%\{[ ]*C\+\+[ ]*\n(?P<cdata>.*?\n?)%\}[ ]*(C\+\+)?"
+        r"%\{[ ]*C\+\+[ ]*\n(?P<cdata>(\n|.)*?\n?)%\}[ ]*(C\+\+)?"
         t.type = "CDATA"
         t.value = t.lexer.lexmatch.group("cdata")
         t.lexer.lineno += t.value.count("\n")
         return t
 
     def t_INCLUDE(self, t):
         r'\#include[ \t]+"[^"\n]+"'
         inc, value, end = t.value.split('"')