pcg: Make MSVC compatible

Still passes all tests of the test suite except for the tests for
a particular class size, which is an odd thing to test for anyway.

thirdparty/pcg/pcg_extras.hpp

@@ -21,6 +21,11 @@
  *     http://www.pcg-random.org
  */
 
+/*
+ * Modified by The OpenClonk.org Project to improve compatibility with
+ * Microsoft Visual C++.
+ */
+
 /*
  * This file provides support code that is useful for random-number generation
  * but not specific to the PCG generation scheme, including:
@@ -58,8 +63,10 @@
 
 #ifdef __GNUC__
     #define PCG_NOINLINE __attribute__((noinline))
+	#define PCG_ALWAYS_INLINE __attribute__((always_inline))
 #else
     #define PCG_NOINLINE
+	#define PCG_ALWAYS_INLINE
 #endif
 
 /*

thirdparty/pcg/pcg_random.hpp

@@ -21,6 +21,11 @@
  *     http://www.pcg-random.org
  */
 
+/*
+ * Modified by The OpenClonk.org Project to improve compatibility with
+ * Microsoft Visual C++.
+ */
+
 /*
  * This code provides the reference implementation of the PCG family of
  * random number generators.  The code is complex because it implements
@@ -1203,7 +1208,7 @@ public:
         return baseclass::period_pow2() + table_size*extvalclass::period_pow2();
     }
 
-    __attribute__((always_inline)) result_type operator()()
+    PCG_ALWAYS_INLINE result_type operator()()
     {
         result_type rhs = get_extended_value();
         result_type lhs = this->baseclass::operator()();

thirdparty/pcg/pcg_uint128.hpp

@@ -21,6 +21,11 @@
  *     http://www.pcg-random.org
  */
 
+/*
+ * Modified by The OpenClonk.org Project to improve compatibility with
+ * Microsoft Visual C++.
+ */
+
 /*
  * This code provides a a C++ class that can provide 128-bit (or higher)
  * integers.  To produce 2K-bit integers, it uses two K-bit integers,
@@ -65,7 +70,8 @@
         #define PCG_LITTLE_ENDIAN 1
     #elif __BIG_ENDIAN__ || _BIG_ENDIAN
         #define PCG_LITTLE_ENDIAN 0
-    #elif __x86_64 || __x86_64__ || __i386 || __i386__
+    #elif __x86_64 || __x86_64__ || __i386 || __i386__ \
+          || _M_X64 || _M_IX86 || _M_ARM || _M_IA64
         #define PCG_LITTLE_ENDIAN 1
     #elif __powerpc__ || __POWERPC__ || __ppc__ || __PPC__ \
           || __m68k__ || __mc68000__