Changed multi-line C comments into another style.

The left side doesn't look unbalanced.

src/ld65/cfgexpr.h

@@ -57,8 +57,8 @@ long CfgConstExpr (void);
 
 long CfgCheckedConstExpr (long Min, long Max);
 /* Read an expression, make sure it's an int and in range, then return its
- * value.
- */
+** value.
+*/