Fix incompatible pointer type errors from GCC 15

[andersk]

gcc -W -Wall -O3 -DNLGLOG -DNDEBUG -DNCHKSOL -DNLGLDRUPLIG -DNLGLYALSAT -DNLGLFILES -DNLGLDEMA -c treengeling.c
treengeling.c: In function ‘initroot’:
treengeling.c:821:26: error: passing argument 2 of ‘lglsetmsglock’ from incompatible pointer type [-Wincompatible-pointer-types]
  821 |     lglsetmsglock (root, lockmsg, unlockmsg, 0);
      |                          ^~~~~~~
      |                          |
      |                          void (*)(void)
In file included from treengeling.c:5:
lglib.h:346:35: note: expected ‘void (*)(void *)’ but argument is of type ‘void (*)(void)’
  346 | void lglsetmsglock (LGL *, void (*lock)(void*), void (*unlock)(void*), void*);
      |                            ~~~~~~~^~~~~~~~~~~~
treengeling.c:260:15: note: ‘lockmsg’ declared here
  260 |   static void lock ## NAME () { \
      |               ^~~~
treengeling.c:272:1: note: in expansion of macro ‘LOCK’
  272 | LOCK (msg)
      | ^~~~
treengeling.c:821:35: error: passing argument 3 of ‘lglsetmsglock’ from incompatible pointer type [-Wincompatible-pointer-types]
  821 |     lglsetmsglock (root, lockmsg, unlockmsg, 0);
      |                                   ^~~~~~~~~
      |                                   |
      |                                   void (*)(void)
lglib.h:346:56: note: expected ‘void (*)(void *)’ but argument is of type ‘void (*)(void)’
  346 | void lglsetmsglock (LGL *, void (*lock)(void*), void (*unlock)(void*), void*);
      |                                                 ~~~~~~~^~~~~~~~~~~~~~
treengeling.c:264:15: note: ‘unlockmsg’ declared here
  264 |   static void unlock ## NAME () { \
      |               ^~~~~~
treengeling.c:285:1: note: in expansion of macro ‘UNLOCK’
  285 | UNLOCK (msg)
      | ^~~~~~
treengeling.c: In function ‘newnode’:
treengeling.c:860:28: error: passing argument 2 of ‘lglsetmsglock’ from incompatible pointer type [-Wincompatible-pointer-types]
  860 |   lglsetmsglock (res->lgl, lockmsg, unlockmsg, 0);
      |                            ^~~~~~~
      |                            |
      |                            void (*)(void)
lglib.h:346:35: note: expected ‘void (*)(void *)’ but argument is of type ‘void (*)(void)’
  346 | void lglsetmsglock (LGL *, void (*lock)(void*), void (*unlock)(void*), void*);
      |                            ~~~~~~~^~~~~~~~~~~~
treengeling.c:260:15: note: ‘lockmsg’ declared here
  260 |   static void lock ## NAME () { \
      |               ^~~~
treengeling.c:272:1: note: in expansion of macro ‘LOCK’
  272 | LOCK (msg)
      | ^~~~
treengeling.c:860:37: error: passing argument 3 of ‘lglsetmsglock’ from incompatible pointer type [-Wincompatible-pointer-types]
  860 |   lglsetmsglock (res->lgl, lockmsg, unlockmsg, 0);
      |                                     ^~~~~~~~~
      |                                     |
      |                                     void (*)(void)
lglib.h:346:56: note: expected ‘void (*)(void *)’ but argument is of type ‘void (*)(void)’
  346 | void lglsetmsglock (LGL *, void (*lock)(void*), void (*unlock)(void*), void*);
      |                                                 ~~~~~~~^~~~~~~~~~~~~~
treengeling.c:264:15: note: ‘unlockmsg’ declared here
  264 |   static void unlock ## NAME () { \
      |               ^~~~~~
treengeling.c:285:1: note: in expansion of macro ‘UNLOCK’
  285 | UNLOCK (msg)
      | ^~~~~~
treengeling.c: In function ‘startparallel’:
treengeling.c:1043:32: error: passing argument 2 of ‘lglsetmsglock’ from incompatible pointer type [-Wincompatible-pointer-types]
 1043 |   lglsetmsglock (parallel.lgl, lockmsg, unlockmsg, 0);
      |                                ^~~~~~~
      |                                |
      |                                void (*)(void)
lglib.h:346:35: note: expected ‘void (*)(void *)’ but argument is of type ‘void (*)(void)’
  346 | void lglsetmsglock (LGL *, void (*lock)(void*), void (*unlock)(void*), void*);
      |                            ~~~~~~~^~~~~~~~~~~~
treengeling.c:260:15: note: ‘lockmsg’ declared here
  260 |   static void lock ## NAME () { \
      |               ^~~~
treengeling.c:272:1: note: in expansion of macro ‘LOCK’
  272 | LOCK (msg)
      | ^~~~
treengeling.c:1043:41: error: passing argument 3 of ‘lglsetmsglock’ from incompatible pointer type [-Wincompatible-pointer-types]
 1043 |   lglsetmsglock (parallel.lgl, lockmsg, unlockmsg, 0);
      |                                         ^~~~~~~~~
      |                                         |
      |                                         void (*)(void)
lglib.h:346:56: note: expected ‘void (*)(void *)’ but argument is of type ‘void (*)(void)’
  346 | void lglsetmsglock (LGL *, void (*lock)(void*), void (*unlock)(void*), void*);
      |                                                 ~~~~~~~^~~~~~~~~~~~~~
treengeling.c:264:15: note: ‘unlockmsg’ declared here
  264 |   static void unlock ## NAME () { \
      |               ^~~~~~
treengeling.c:285:1: note: in expansion of macro ‘UNLOCK’
  285 | UNLOCK (msg)
      | ^~~~~~
make: *** [makefile:53: treengeling.o] Error 1