emulators/dosbox-x: Fix build with libc++ 19

As noted in the libc++ 19 release notes [1], std::char_traits<> is now
only provided for char, char8_t, char16_t, char32_t and wchar_t, and any
instantiation for other types will fail.

This causes emulators/dosbox-x to fail to compile with clang 19 and
libc++ 19, resulting in errors similar to:

  /usr/include/c++/v1/string:820:42: error: implicit instantiation of undefined template 'std::char_traits<unsigned short>'
    820 |   static_assert(is_same<_CharT, typename traits_type::char_type>::value,
        |                                          ^
  dos_programs.cpp:7692:17: note: in instantiation of template class 'std::basic_string<unsigned short>' requested here
   7692 |     test_string dst;
        |                 ^
  /usr/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
     23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
        |                             ^
  dos_programs.cpp:8893:14: warning: variable 'open' set but not used [-Wunused-but-set-variable]
   8893 |         bool open=false;
        |              ^

This can be fixed by using char16_t for the 'test_char_t` type, and by
adding a few inline wrappers to perform the required casting.

[1] https://libcxx.llvm.org/ReleaseNotes/19.html#deprecations-and-removals

PR:		282386
MFH:		2024Q4

Author: DimitryAndric

emulators/dosbox-x/files/patch-src_dos_dos__programs.cpp

@@ -0,0 +1,24 @@
+Fix build with clang 19
+https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=282386
+
+--- src/dos/dos_programs.cpp.orig	2024-10-02 06:16:36 UTC
++++ src/dos/dos_programs.cpp
+@@ -81,7 +81,7 @@ host_cnv_char_t *CodePageGuestToHost(const char *s);
+ #endif
+ #ifdef C_ICONV
+ #include "iconvpp.hpp"
+-typedef uint16_t test_char_t;
++typedef char16_t test_char_t;
+ typedef std::basic_string<test_char_t> test_string;
+ typedef std::basic_string<char> test_char;
+ #endif
+@@ -102,6 +102,9 @@ bool CodePageHostToGuestUTF8(char *d/*CROSS_LEN*/,cons
+ bool qmount = false;
+ bool nowarn = false;
+ bool CodePageHostToGuestUTF8(char *d/*CROSS_LEN*/,const char *s/*CROSS_LEN*/), CodePageHostToGuestUTF16(char *d/*CROSS_LEN*/,const uint16_t *s/*CROSS_LEN*/);
++inline bool CodePageHostToGuestUTF16(char *d/*CROSS_LEN*/,const char16_t *s/*CROSS_LEN*/) {
++    return CodePageHostToGuestUTF16(d, reinterpret_cast<const uint16_t *>(s));
++}
+ extern bool systemmessagebox(char const * aTitle, char const * aMessage, char const * aDialogType, char const * aIconType, int aDefaultButton);
+ extern bool addovl, addipx, addne2k, prepared, inshell, usecon, uao, loadlang, morelen, mountfro[26], mountiro[26], resetcolor, staycolors, printfont, notrycp, internal_program;
+ extern bool clear_screen(), OpenGL_using(void), DOS_SetAnsiAttr(uint8_t attr), isDBCSCP();

emulators/dosbox-x/files/patch-src_dos_drive__iso.cpp

@@ -0,0 +1,34 @@
+Fix build with clang 19
+https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=282386
+
+--- src/dos/drive_iso.cpp.orig	2024-10-02 06:16:36 UTC
++++ src/dos/drive_iso.cpp
+@@ -40,6 +40,10 @@ extern bool CodePageHostToGuestUTF16(char *d/*CROSS_LE
+ extern bool gbk, isDBCSCP(), isKanji1_gbk(uint8_t chr), shiftjis_lead_byte(int c);
+ extern bool filename_not_8x3(const char *n), filename_not_strict_8x3(const char *n);
+ extern bool CodePageHostToGuestUTF16(char *d/*CROSS_LEN*/,const uint16_t *s/*CROSS_LEN*/);
++inline bool CodePageHostToGuestUTF16(uint8_t *d/*CROSS_LEN*/,const uint8_t *s/*CROSS_LEN*/) {
++    std::u16string u16s(reinterpret_cast<const char16_t *>(s));
++    return CodePageHostToGuestUTF16(reinterpret_cast<char *>(d), reinterpret_cast<const uint16_t *>(u16s.c_str()));
++}
+ 
+ using namespace std;
+ 
+@@ -1762,7 +1766,7 @@ int isoDrive::readDirEntry(isoDirEntry* de, const uint
+ 				// The string is big Endian UCS-16, convert to host Endian UCS-16
+ 				for (size_t i=0;((const uint16_t*)de->ident)[i] != 0;i++) ((uint16_t*)de->ident)[i] = be16toh(((uint16_t*)de->ident)[i]);
+ 				// finally, convert from UCS-16 to local code page, using C++ string construction to make a copy first
+-				CodePageHostToGuestUTF16((char*)de->ident,std::basic_string<uint16_t>((const uint16_t*)de->ident).c_str());
++				CodePageHostToGuestUTF16(de->ident, de->ident);
+ 			}
+ 		}
+ 	} else {
+@@ -1784,7 +1788,7 @@ int isoDrive::readDirEntry(isoDirEntry* de, const uint
+ 			// The string is big Endian UCS-16, convert to host Endian UCS-16
+ 			for (size_t i=0;((const uint16_t*)de->ident)[i] != 0;i++) ((uint16_t*)de->ident)[i] = be16toh(((uint16_t*)de->ident)[i]);
+ 			// finally, convert from UCS-16 to local code page, using C++ string construction to make a copy first
+-			CodePageHostToGuestUTF16((char*)de->ident,std::basic_string<uint16_t>((const uint16_t*)de->ident).c_str());
++			CodePageHostToGuestUTF16(de->ident, de->ident);
+ 		}
+ 		else {
+ 			// remove any file version identifiers as there are some cdroms that don't have them