science/kst2: fix build with C++17

Drop register keyword to fix build with clang16.

science/kst2/files/patch-src_libkstmath_escan.cpp

+--- src/libkstmath/escan.cpp.orig	2022-02-16 19:03:30 UTC
++++ src/libkstmath/escan.cpp
+@@ -691,9 +691,9 @@ extern int yylex (void);
+  */
+ YY_DECL
+ {
+-	register yy_state_type yy_current_state;
+-	register char *yy_cp, *yy_bp;
+-	register int yy_act;
++	yy_state_type yy_current_state;
++	char *yy_cp, *yy_bp;
++	int yy_act;
+     
+ #line 21 "escan.l"
+ 
+@@ -742,7 +742,7 @@ YY_DECL
+ yy_match:
+ 		do
+ 			{
+-			register YY_CHAR yy_c = yy_ec[YY_SC_TO_UI(*yy_cp)];
++			YY_CHAR yy_c = yy_ec[YY_SC_TO_UI(*yy_cp)];
+ 			if ( yy_accept[yy_current_state] )
+ 				{
+ 				(yy_last_accepting_state) = yy_current_state;
+@@ -1130,9 +1130,9 @@ ECHO;
+  */
+ static int yy_get_next_buffer (void)
+ {
+-    	register char *dest = YY_CURRENT_BUFFER_LVALUE->yy_ch_buf;
+-	register char *source = (yytext_ptr);
+-	register int number_to_move, i;
++    	char *dest = YY_CURRENT_BUFFER_LVALUE->yy_ch_buf;
++	char *source = (yytext_ptr);
++	int number_to_move, i;
+ 	int ret_val;
+ 
+ 	if ( (yy_c_buf_p) > &YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[(yy_n_chars) + 1] )
+@@ -1264,14 +1264,14 @@ static int yy_get_next_buffer (void)
+ 
+     static yy_state_type yy_get_previous_state (void)
+ {
+-	register yy_state_type yy_current_state;
+-	register char *yy_cp;
++	yy_state_type yy_current_state;
++	char *yy_cp;
+     
+ 	yy_current_state = (yy_start);
+ 
+ 	for ( yy_cp = (yytext_ptr) + YY_MORE_ADJ; yy_cp < (yy_c_buf_p); ++yy_cp )
+ 		{
+-		register YY_CHAR yy_c = (*yy_cp ? yy_ec[YY_SC_TO_UI(*yy_cp)] : 1);
++		YY_CHAR yy_c = (*yy_cp ? yy_ec[YY_SC_TO_UI(*yy_cp)] : 1);
+ 		if ( yy_accept[yy_current_state] )
+ 			{
+ 			(yy_last_accepting_state) = yy_current_state;
+@@ -1296,10 +1296,10 @@ static int yy_get_next_buffer (void)
+  */
+     static yy_state_type yy_try_NUL_trans  (yy_state_type yy_current_state )
+ {
+-	register int yy_is_jam;
+-    	register char *yy_cp = (yy_c_buf_p);
++	int yy_is_jam;
++    	char *yy_cp = (yy_c_buf_p);
+ 
+-	register YY_CHAR yy_c = 1;
++	YY_CHAR yy_c = 1;
+ 	if ( yy_accept[yy_current_state] )
+ 		{
+ 		(yy_last_accepting_state) = yy_current_state;
+@@ -1317,9 +1317,9 @@ static int yy_get_next_buffer (void)
+ 	return yy_is_jam ? 0 : yy_current_state;
+ }
+ #if 0
+-    static void yyunput (int c, register char * yy_bp )
++    static void yyunput (int c, char * yy_bp )
+ {
+-	register char *yy_cp;
++	char *yy_cp;
+     
+     yy_cp = (yy_c_buf_p);
+ 
+@@ -1329,10 +1329,10 @@ static int yy_get_next_buffer (void)
+ 	if ( yy_cp < YY_CURRENT_BUFFER_LVALUE->yy_ch_buf + 2 )
+ 		{ /* need to shift things up to make room */
+ 		/* +2 for EOB chars. */
+-		register int number_to_move = (yy_n_chars) + 2;
+-		register char *dest = &YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[
++		int number_to_move = (yy_n_chars) + 2;
++		char *dest = &YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[
+ 					YY_CURRENT_BUFFER_LVALUE->yy_buf_size + 2];
+-		register char *source =
++		char *source =
+ 				&YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[number_to_move];
+ 
+ 		while ( source > YY_CURRENT_BUFFER_LVALUE->yy_ch_buf )
+@@ -1953,7 +1953,7 @@ int yylex_destroy  (void)
+ #ifndef yytext_ptr
+ static void yy_flex_strncpy (char* s1, yyconst char * s2, int n )
+ {
+-	register int i;
++	int i;
+ 	for ( i = 0; i < n; ++i )
+ 		s1[i] = s2[i];
+ }
+@@ -1962,7 +1962,7 @@ static void yy_flex_strncpy (char* s1, yyconst char * 
+ #ifdef YY_NEED_STRLEN
+ static int yy_flex_strlen (yyconst char * s )
+ {
+-	register int n;
++	int n;
+ 	for ( n = 0; s[n]; ++n )
+ 		;
+