Speed up EPG loading

With #269 there are three regex which are evaluated on every function call. In my case loading time was increased from 800msec to 10sec. This PR replaces those regex with static one and brings time down to 530msec.

pvr.iptvsimple/addon.xml.in

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <addon
   id="pvr.iptvsimple"
-  version="3.8.2"
+  version="3.8.3"
   name="PVR IPTV Simple Client"
   provider-name="nightik">
   <requires>@ADDON_DEPENDS@</requires>

pvr.iptvsimple/changelog.txt

@@ -1,3 +1,6 @@
+v3.8.3
+- Speed up EPG loading
+
 v3.8.2
 - Update github wiki link in addon.xml
 

src/PVRIptvData.cpp

@@ -419,7 +419,8 @@ bool PVRIptvData::LoadEPG(time_t iStart, time_t iEnd)
     GetNodeValue(pChannelNode, "date", dateString);
     if (!dateString.empty())
     {
-      if (std::regex_match(dateString, std::regex("^[1-9][0-9][0-9][0-9][0-9][1-9][0-9][1-9]")))
+      static const std::regex dateRegex("^[1-9][0-9][0-9][0-9][0-9][1-9][0-9][1-9]");
+      if (std::regex_match(dateString, dateRegex))
         entry.firstAired = static_cast<time_t>(ParseDateTime(dateString));
 
       std::sscanf(dateString.c_str(), "%04d", &entry.iYear);
@@ -534,10 +535,12 @@ bool PVRIptvData::ParseXmltvNsEpisodeNumberInfo(const std::string& episodeNumber
 
 bool PVRIptvData::ParseOnScreenEpisodeNumberInfo(const std::string& episodeNumberString, PVRIptvEpgEntry& entry)
 {
-  const std::string text = std::regex_replace(episodeNumberString, std::regex("[ \\txX_\\.]"), "");
+  static const std::regex numRegex("[ \\txX_\\.]");
+  const std::string text = std::regex_replace(episodeNumberString, numRegex, "");
 
   std::smatch match;
-  if (std::regex_match(text, match, std::regex("^[sS]([0-9][0-9]*)[eE][pP]?([0-9][0-9]*)$")))
+  static const std::regex epRegex("^[sS]([0-9][0-9]*)[eE][pP]?([0-9][0-9]*)$");
+  if (std::regex_match(text, match, epRegex))
   {
     if (match.size() == 3)
     {