doc: Drop hint at --enable-memalign-hack for MinGW, it is now autodetected.

doc/general.texi

@@ -831,18 +831,6 @@ are listed below:
 Libav automatically passes @code{-fno-common} to the compiler to work around
 a GCC bug (see @url{http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37216}).
 
-Within the MSYS shell, configure and make with:
-
-@example
-./configure --enable-memalign-hack
-make
-make install
-@end example
-
-This will install @file{ffmpeg.exe} along with many other development files
-to @file{/usr/local}. You may specify another install path using the
-@code{--prefix} option in @file{configure}.
-
 Notes:
 
 @itemize