bug#15212: 24.3.50; c++-mode doesn't support raw string literals

[Michael Welsh Duggan]

Since you are working on string handling I thought I would verify
whether you handle the following:

Every string literal, including raw string literals, may be proceeded by
an encoding-prefix (no space separating).  The valid encoding-prefixes
are:

u8 u U L

Examples from the standard:

"..."
R"(...)"
u8"..."
u8R"**(...)**"
u"..."
uR"*~(..)*~"
U"..."
UR"zzz(...)zzz"
L"..."
LR"(...)"

The meanings of these prefixes are:

u8: UTF-8 string literal
u:  char16_t literal
U:  char32_t literal
L:  wchar_t literal

-- 
Michael Welsh Duggan
(md5i@md5i.com)