mosml-dynlibs does not build: lvalue required as left operand of assignment

[ryandesign (Ryan Carsten Schmidt)]

msocket.c: In function ‘newsocket’:
msocket.c:114: error: lvalue required as left operand of assignment

[barracuda156]

Ha, I thought this error was fixed in the source, but no: while gcc-4.2 builds it fine, gcc-12 errs out, like clang.

make[1]: Entering directory `/opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_lang_mosml/mosml-dynlibs/work/mosml-13c581aec46eea134e478f2e2b6456278e36ecce/src/dynlibs/mmysql'
/opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_lang_mosml/mosml-dynlibs/work/compwrap/cc/opt/local/bin/gcc-mp-12 -Dunix -O2 -fno-defer-pop -I/opt/local/include/mosml -I /opt/local/include/mysql57/mysql -c -o mmysql.o mmysql.c
mmysql.c: In function 'dbresult_finalize':
mmysql.c:79:28: error: lvalue required as left operand of assignment
   79 |     DBresult_val(dbresval) = NULL;
      |                            ^
mmysql.c:81:33: error: lvalue required as left operand of assignment
   81 |     DBresultindex_val(dbresval) = NULL;
      |                                 ^

[barracuda156]

In a88d61b32b0cfbcbc9cf3537b232cc1c6953dcf2/macports-ports (master):

mosml: update to latest upstream, make -dynlibs its subport, close a bunch of old tickets

Closes: #39662
Closes: #58503
Fixes: #39665
Fixes: #39664