Add seedable PRNG using an adaptation the original LCG algorithm.

main.h

@@ -2,9 +2,15 @@
 
 #define LINESIZE	100
 
+typedef struct lcg_state
+{
+  unsigned long a, c, m, x;
+} lcg_state;
+
 extern long ABB[], ATAB[], ATLOC[], BLKLIN, DFLAG, DLOC[], FIXED[], HOLDNG,
 		KTAB[], *LINES, LINK[], LNLENG, LNPOSN,
 		PARMS[], PLACE[], PTEXT[], RTEXT[], TABSIZ;
 extern signed char INLINE[LINESIZE+1], MAP1[], MAP2[];
 extern FILE *logfp;
 extern bool oldstyle;
+extern lcg_state lcgstate;