Fix #121: DMD not required, should the README change?

This adds support for building with LDC. Building with LDC will make
it possible to create a fully statically linked binary for Linux and,
possible, FreeBSD.

Author: jacob-carlborg

.travis.yml

@@ -2,6 +2,8 @@ language: d
 d:
   - dmd-2.072.2
   - dmd-2.071.2
+  - ldc
+  - ldc-beta
 
 before_script: git fetch --unshallow
 script: "dub --config=test"

README.markdown

@@ -26,8 +26,8 @@ The source code is available under the [Boost Software License 1.0](http://www.b
 #### Requirements
 
 * libclang - [http://clang.llvm.org](http://clang.llvm.org) - 3.4 or later that is binary compatible with 3.4
-* DMD - [http://dlang.org/download.html](http://dlang.org/download.html) - 2.071.2 or later
-* Dub [http://code.dlang.org/download](http://code.dlang.org/download)
+* A D compiler - [DMD](http://dlang.org/download.html) 2.071.2 or later or [LDC](https://github.com/ldc-developers/ldc/releases/tag/v1.2.0) 1.2.0 or later
+* Dub [http://code.dlang.org/download](http://code.dlang.org/download) (also shipped with the compilers)
 
 #### Building
 

dstep/translator/IncludeHandler.d

@@ -21,9 +21,9 @@ class IncludeHandler
     private string[string] submodules;
     private bool[string] includes;
     private bool[string] imports;
-    static string[string] knownIncludes;
+    immutable static string[string] knownIncludes;
 
-    static this ()
+    shared static this ()
     {
         knownIncludes = [
             "complex" : "core.stdc.complex",