solvers: Fix incorrect f_OPHOL declaration

Author: Tatsh

src/solvers/fgh_read.c

@@ -98,7 +98,7 @@ sorry_CLP(EdRead *R, const char *what)
 #define memadj(x) (((x) + (sizeof(long)-1)) & ~(sizeof(long)-1))
 #endif
 
- extern char* f_OPHOL;
+ extern char *f_OPHOL ANSI((expr *e));
  extern efunc f_OPPLTERM, f_OPVARVAL, f_OPFUNCALL;
  extern sfunc f_OPIFSYM;