Read timeout for modules that immediately spit out data (no buffer)

They do need a millis() based timeout so that data left in the buffer after the socket closes can still be read in but the maintain doesn't sit and wait forever.

src/TinyGsmClientA6.h

@@ -121,7 +121,8 @@ public:
   virtual int read(uint8_t *buf, size_t size) {
     TINY_GSM_YIELD();
     size_t cnt = 0;
-    while (cnt < size && sock_connected) {
+    uint32_t _startMillis = millis();
+    while (cnt < size && millis() - _startMillis < _timeout) {
       size_t chunk = TinyGsmMin(size-cnt, rx.size());
       if (chunk > 0) {
         rx.get(buf, chunk);
@@ -130,7 +131,7 @@ public:
         continue;
       }
       // TODO: Read directly into user buffer?
-      if (!rx.size()) {
+      if (!rx.size() && sock_connected) {
         at->maintain();
       }
     }

src/TinyGsmClientESP8266.h

@@ -118,7 +118,8 @@ public:
   virtual int read(uint8_t *buf, size_t size) {
     TINY_GSM_YIELD();
     size_t cnt = 0;
-    while (cnt < size && sock_connected) {
+    uint32_t _startMillis = millis();
+    while (cnt < size && millis() - _startMillis < _timeout) {
       size_t chunk = TinyGsmMin(size-cnt, rx.size());
       if (chunk > 0) {
         rx.get(buf, chunk);
@@ -127,7 +128,7 @@ public:
         continue;
       }
       // TODO: Read directly into user buffer?
-      if (!rx.size()) {
+      if (!rx.size() && sock_connected) {
         at->maintain();
       }
     }

src/TinyGsmClientM590.h

@@ -118,7 +118,8 @@ public:
   virtual int read(uint8_t *buf, size_t size) {
     TINY_GSM_YIELD();
     size_t cnt = 0;
-    while (cnt < size && sock_connected) {
+    uint32_t _startMillis = millis();
+    while (cnt < size && millis() - _startMillis < _timeout) {
       size_t chunk = TinyGsmMin(size-cnt, rx.size());
       if (chunk > 0) {
         rx.get(buf, chunk);