[MINOR] pattern: make the converter more flexible by supporting void* and int args

The pattern type converters currently support a string arg and a length.
Sometimes we'll prefer to pass them a list or a structure. So let's convert
the string and length into a generic void* and int that each converter may
use as it likes.
diff --git a/include/types/pattern.h b/include/types/pattern.h
index c6f8ec8..811625e 100644
--- a/include/types/pattern.h
+++ b/include/types/pattern.h
@@ -54,8 +54,8 @@
 /* pattern conversion */
 struct pattern_conv {
 	const char *kw;                           /* configuration keyword  */
-	int (*process)(const char *arg,
-	               int arg_len,
+	int (*process)(const void *arg_p,
+	               int arg_i,
 	               union pattern_data *data); /* process function */
 	unsigned int in_type;                     /* input needed pattern type */
 	unsigned int out_type;                    /* output pattern type */
@@ -65,8 +65,8 @@
 struct pattern_conv_expr {
 	struct list list;                         /* member of a pattern expression */
 	struct pattern_conv *conv;                /* pattern conversion */
-	char *arg;                                /* configured keyword argument */
-	int arg_len;                              /* configured keyword argument length */
+	void *arg_p;                              /* pointer arg, most often a string argument */
+	int arg_i;                                /* int arg, most often the argument's length */
 };
 
 /* pattern fetch */
diff --git a/src/pattern.c b/src/pattern.c
index c593404..a5cb31f 100644
--- a/src/pattern.c
+++ b/src/pattern.c
@@ -432,10 +432,9 @@
 		conv_expr->conv = conv;
 
 		if (end != endw) {
-			conv_expr->arg_len = end - endw - 2;
-			conv_expr->arg = malloc(conv_expr->arg_len + 1);
-			conv_expr->arg = memcpy(conv_expr->arg, endw + 1, conv_expr->arg_len);
-			conv_expr->arg[expr->arg_len] = '\0';
+			conv_expr->arg_i = end - endw - 2;
+			conv_expr->arg_p = calloc(1, conv_expr->arg_i + 1);
+			memcpy(conv_expr->arg_p, endw + 1, conv_expr->arg_i);
 		}
 	}
 	return expr;
@@ -471,7 +470,7 @@
 			return NULL;
 
 		p->type = conv_expr->conv->in_type;
-		if (!conv_expr->conv->process(conv_expr->arg, conv_expr->arg_len, &p->data))
+		if (!conv_expr->conv->process(conv_expr->arg_p, conv_expr->arg_i, &p->data))
 			return NULL;
 
 		p->type = conv_expr->conv->out_type;
@@ -532,7 +531,7 @@
 /*    Pattern format convert functions                           */
 /*****************************************************************/
 
-static int pattern_conv_str2lower(const char *arg, int arg_len, union pattern_data *data)
+static int pattern_conv_str2lower(const void *arg_p, int arg_i, union pattern_data *data)
 {
 	int i;
 
@@ -543,7 +542,7 @@
 	return 1;
 }
 
-static int pattern_conv_str2upper(const char *arg, int arg_len, union pattern_data *data)
+static int pattern_conv_str2upper(const void *arg_p, int arg_i, union pattern_data *data)
 {
 	int i;