http: fix gcc 3.x build, don't use always_inline

src/node_http_parser.cc

@@ -103,8 +103,14 @@ static char* current_buffer_data;
 static size_t current_buffer_len;
 
 
+// gcc 3.x knows the always_inline attribute but fails at build time with a
+// "sorry, unimplemented: inlining failed" error when compiling at -O0
 #if defined(__GNUC__)
+# if __GNUC__ >= 4
 #  define always_inline __attribute__((always_inline))
+# else
+#  define always_inline inline
+# endif
 #elif defined(_MSC_VER)
 # define always_inline __forceinline
 #else