travis: add gcc 4.4, 4.6 and 4.7

.travis.yml

@@ -6,6 +6,42 @@ matrix:
     allow_failures:
         compiler: gcc-6
     include:
+        - os: linux
+          addons:
+            apt:
+              packages:
+              - gcc-4.4
+              - libsdl2-mixer-dev
+              - libpng-dev
+              - libgl1-mesa-dev
+              - libgme-dev
+              - p7zip-full
+          compiler: gcc-4.4
+          #gcc-4.4
+        - os: linux
+          addons:
+            apt:
+              packages:
+              - gcc-4.6
+              - libsdl2-mixer-dev
+              - libpng-dev
+              - libgl1-mesa-dev
+              - libgme-dev
+              - p7zip-full
+          compiler: gcc-4.6
+          #gcc-4.6
+        - os: linux
+          addons:
+            apt:
+              packages:
+              - gcc-4.7
+              - libsdl2-mixer-dev
+              - libpng-dev
+              - libgl1-mesa-dev
+              - libgme-dev
+              - p7zip-full
+          compiler: gcc-4.7
+          #gcc-4.7
         - os: linux
           compiler: gcc
           #gcc (Ubuntu 4.8.4-2ubuntu1~14.04) 4.8.4

src/sdl/i_main.c

@@ -245,7 +245,7 @@ int main(int argc, char **argv)
 #endif
 
 	// return to OS
-#if !defined (__GNUC__) || (__GNUC__ < 4)
+#if !defined (__GNUC__) || (__GNUC__ < 3)
 	return 0;
 #endif
 }