mingw32: Enable wintls and compile with GMP

By enabling wintls, we can use Windows certificate store to validate
server's certificate.  Previously, we built windows build using
openssl and since we don't bundle CA certificates, aria2 fails to
validate server's certificate unless user setups their CA
certificates.  GMP provides fast big integer calculations, whic is
used in BitTorrent encryption.

README.mingw

@@ -12,7 +12,7 @@ Debian Linux.
 The executable is statically linked, so no extra DLLs are
 necessary. The linked libraries are:
 
-* openssl 1.0.1g
+* gmp 6.0.0
 * expat 2.1.0
 * sqlite 3.8.4.1
 * zlib 1.2.8

mingw-build-memo

@@ -7,6 +7,22 @@ HOST=i686-w64-mingw32
 HOST=x86_64-w64-mingw32
 ./Configure --cross-compile-prefix=$HOST- --prefix=/usr/local/$HOST mingw64
 
+GMP
+---
+
+HOST=i686-w64-mingw32
+./configure \
+    --disable-shared \
+    --enable-static \
+    --prefix=/usr/local/$HOST \
+    --host=$HOST \
+    --disable-cxx \
+    --enable-fat \
+    CFLAGS="-mtune=generic -O2 -g0"
+
+HOST=x86_64-w64-mingw32
+The configure command-line is the same as i686 version.
+
 Sqlite
 ------
 

mingw-config

@@ -48,7 +48,7 @@
 # In this configuration, the following dependent libraries are used:
 #
 # * c-ares
-# * openssl
+# * gmp
 # * expat
 # * sqlite3
 # * zlib
@@ -63,12 +63,14 @@ test -z "$PREFIX" && PREFIX=/usr/local/$HOST
     --without-included-gettext \
     --disable-nls \
     --with-libcares \
+    --with-wintls \
     --without-gnutls \
-    --with-openssl \
+    --without-openssl \
     --with-sqlite3 \
     --without-libxml2 \
     --with-libexpat \
     --with-libz \
+    --with-libgmp \
     --without-libgcrypt \
     --without-libnettle \
     --with-cppunit-prefix=$PREFIX \