Enable strings as parameters across subckt boundaries

by keeping the quotes and excluding {} around the string token.

src/frontend/inpcom.c

@@ -3304,7 +3304,12 @@ void inp_casefix(char *string)
             tmpstr = strstr(string, "file=\"");
 
 #endif
-        keepquotes = ciprefix(".param", string); // Allow string params
+        /* Allow string params */
+        keepquotes = ciprefix(".param", string);
+        /* Allow string param in .subckt lines */
+        keepquotes = keepquotes || (ciprefix(".subckt", string) && (strstr(string, "=\"")));
+        /* Keep quoted strings in X lines */
+        keepquotes = keepquotes || (*string == 'x' && strchr(string, '\"'));
 
         while (*string) {
 #ifdef XSPICE
@@ -3914,7 +3919,8 @@ static int inp_get_params(
         *end = '\0';
 
         if (*value == '{' || isdigit_c(*value) ||
-                (*value == '.' && isdigit_c(value[1]))) {
+                (*value == '.' && isdigit_c(value[1])) ||
+                (*value == '\"')) {
             value = copy(value);
         }
         else {

src/frontend/numparam/xpressn.c

@@ -1623,8 +1623,8 @@ nupa_subcktcall(dico_t *dico, const char *s, const char *x,
                 char *kp = jp;
                 ds_clear(&ustr);
 
-                if (alfanum(*kp) || *kp == '.') {
-                    /* number, identifier */
+                if (alfanum(*kp) || *kp == '.' || *kp == '\"') {
+                    /* number, identifier, string */
                     jp = skip_non_ws(kp);
                     pscopy(&ustr, kp, jp);
                 } else if (*kp == '{') {