irssi: Fix OpenSSL without deprecated APIs compilation

When OpenSSL is built without deprecated APIs, pkg-config first tries
OpenSSL in the staging directory but fails as it cannot find the
deprecated SSL_library_init function and ends up finding the system one.

Added PKG_BUILD_PARALLEL for faster compilation.

Added -Wl,--gc-sections to LDFLAGS to save ~10KB from the resulting ipk.

Reworked configure section as some of those options were renamed or
removed.

Removed EXTRA_* hacks that are no longer necessary.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

net/irssi/patches/010-Fix-finding-OpenSSL-when-1.1-with-deprecated-APIs-di.patch

@@ -0,0 +1,27 @@
+From cff1385b398b59c74c535d6c0cd9deec561101fd Mon Sep 17 00:00:00 2001
+From: Rosen Penev <rosenp@gmail.com>
+Date: Fri, 15 Feb 2019 15:02:34 -0800
+Subject: [PATCH] Fix finding OpenSSL when 1.1 with deprecated APIs disabled
+
+SSL_library_init is a deprecated function. OPENSSL_init_ssl is not in 1.0.2.
+SSL_CTX_new is in both.
+---
+ configure.ac | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/configure.ac b/configure.ac
+index e8290dfd..8dde6095 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -319,7 +319,7 @@ PKG_CHECK_MODULES([OPENSSL], [openssl], [
+ 	CFLAGS="$CFLAGS $OPENSSL_CFLAGS"
+ 	LIBS="$LIBS $OPENSSL_LIBS"
+ ], [
+-	AC_CHECK_LIB([ssl], [SSL_library_init], [
++	AC_CHECK_LIB([ssl], [SSL_CTX_new], [
+ 		LIBS="$LIBS -lssl -lcrypto"
+ 	], [
+ 		AC_MSG_ERROR([The OpenSSL library was not found])
+-- 
+2.17.1
+