Updated xs/Build.PL to support Visual Studio compiler suite.

Updated xs/Build.PL to understand BOOST_LIBRARY_PATH and
BOOST_INCLUDE_PATH environment variables. This way one may easily
switch between various boost builds.

Some minor tweeks were done to make Slic3r compile with
Visual Studio 2013.

xs/src/libslic3r/PlaceholderParser.cpp

@@ -3,14 +3,22 @@
 #include <ctime>
 #include <iomanip>
 #include <sstream>
-#include <unistd.h>  // provides **environ
+#ifdef _MSC_VER
+    #include <stdlib.h>  // provides **_environ
+#else
+    #include <unistd.h>  // provides **environ
+#endif
 
 #ifdef __APPLE__
 #include <crt_externs.h>
 #undef environ
 #define environ (*_NSGetEnviron())
 #else
- 	extern char **environ;
+    #ifdef _MSC_VER
+       #define environ _environ
+    #else
+     	extern char **environ;
+    #endif
 #endif
 
 namespace Slic3r {

xs/src/libslic3r/libslic3r.h

@@ -25,14 +25,17 @@ typedef double coordf_t;
 
 namespace Slic3r {
 
-// TODO: make sure X = 0
-enum Axis { X, Y, Z };
+enum Axis { X=0, Y, Z };
 
 }
 using namespace Slic3r;
 
 /* Implementation of CONFESS("foo"): */
-#define CONFESS(...) confess_at(__FILE__, __LINE__, __func__, __VA_ARGS__)
+#ifdef _MSC_VER
+	#define CONFESS(...) confess_at(__FILE__, __LINE__, __FUNCTION__, __VA_ARGS__)
+#else
+	#define CONFESS(...) confess_at(__FILE__, __LINE__, __func__, __VA_ARGS__)
+#endif
 void confess_at(const char *file, int line, const char *func, const char *pat, ...);
 /* End implementation of CONFESS("foo"): */
 

xs/src/xsinit.h

@@ -40,6 +40,12 @@ extern "C" {
 #include "ppport.h"
 #undef do_open
 #undef do_close
+#ifdef _MSC_VER
+    // Undef some of the macros set by Perl <xsinit.h>, which cause compilation errors on Win32
+    #undef send
+    #undef connect
+    #undef bind
+#endif /* _MSC_VER */
 }
 #endif