Add GSL dependency

.gitmodules

@@ -14,3 +14,6 @@
 	path = deps/HDiffPatch
 	url = https://github.com/sisong/HDiffPatch.git
 	branch = master
+[submodule "deps/GSL"]
+	path = deps/GSL
+	url = https://github.com/Microsoft/GSL.git

deps/GSL

@@ -0,0 +1 @@
+Subproject commit 0f68d133fa6fd2973951b8aaab481e34bbfd2cf4

deps/premake/gsl.lua

@@ -0,0 +1,19 @@
+gsl = {
+	source = path.join(dependencies.basePath, "GSL"),
+}
+
+function gsl.import()
+	gsl.includes()
+end
+
+function gsl.includes()
+	includedirs {
+		path.join(gsl.source, "include")
+	}
+end
+
+function gsl.project()
+
+end
+
+table.insert(dependencies, gsl)

src/std_include.hpp

@@ -41,6 +41,8 @@
 #include <patch.h>
 #include <tomcrypt.h>
 
+#include <gsl/gsl>
+
 #pragma comment (lib, "gdiplus.lib")
 #pragma comment(lib, "ws2_32.lib")