lvm2api: add defined lvm_percent_to_float

Implement function which was somehow missing from it's original
placement in the header file lvm2api.h.

WHATS_NEW

@@ -1,5 +1,6 @@
 Version 2.02.98 -
 =================================
+  Add implementation of lvm2api function lvm_percent_to_float.
   Allow non power of 2 thin chunk sizes if thin pool driver supports that.
   Allow limited metadata changes when PVs are missing via [vg|lv]change.
   Do not start dmeventd for lvchange --resync when monitoring is off.

liblvm/lvm_base.c

@@ -126,3 +126,8 @@ const char *lvm_vgname_from_device(lvm_t libh, const char *device)
 	struct cmd_context *cmd = (struct cmd_context *)libh;
 	return find_vgname_from_pvname(cmd, device);
 }
+
+float lvm_percent_to_float(percent_t v)
+{
+	return percent_to_float(v);
+}