py/misc: Fix msvc and C++ compatibility.

Use explicit casts to suppress warnings about implicit conversions, add a
workaround for constant expression conditional, and make functions static
inline (as is done in the rest of the codebase) to suppress 'warning C4505:
unreferenced function with internal linkage has been removed'.

(Follow up to fix commit 908ab1ce)
Signed-off-by: stijn <stijn@ignitron.net>

py/misc.h

@@ -338,38 +338,44 @@ typedef const char *mp_rom_error_text_t;
 #ifdef _MSC_VER
 #include <intrin.h>
 
-static uint32_t mp_clz(uint32_t x) {
+static inline uint32_t mp_clz(uint32_t x) {
     unsigned long lz = 0;
     return _BitScanReverse(&lz, x) ? (sizeof(x) * 8 - 1) - lz : 0;
 }
 
-static uint32_t mp_clzl(unsigned long x) {
+static inline uint32_t mp_clzl(unsigned long x) {
     unsigned long lz = 0;
     return _BitScanReverse(&lz, x) ? (sizeof(x) * 8 - 1) - lz : 0;
 }
 
 #ifdef _WIN64
-static uint32_t mp_clzll(unsigned long long x) {
+static inline uint32_t mp_clzll(unsigned long long x) {
     unsigned long lz = 0;
     return _BitScanReverse64(&lz, x) ? (sizeof(x) * 8 - 1) - lz : 0;
 }
 #else
 // Microsoft don't ship _BitScanReverse64 on Win32, so emulate it
-static uint32_t mp_clzll(unsigned long long x) {
+static inline uint32_t mp_clzll(unsigned long long x) {
     unsigned long h = x >> 32;
     return h ? mp_clzl(h) : (mp_clzl(x) + 32);
 }
 #endif
 
-static uint32_t mp_ctz(uint32_t x) {
+static inline uint32_t mp_ctz(uint32_t x) {
     unsigned long tz = 0;
     return _BitScanForward(&tz, x) ? tz : 0;
 }
+
+// Workaround for 'warning C4127: conditional expression is constant'.
+static inline bool mp_check(bool value) {
+    return value;
+}
 #else
 #define mp_clz(x) __builtin_clz(x)
 #define mp_clzl(x) __builtin_clzl(x)
 #define mp_clzll(x) __builtin_clzll(x)
 #define mp_ctz(x) __builtin_ctz(x)
+#define mp_check(x) (x)
 #endif
 
 // mp_int_t can be larger than long, i.e. Windows 64-bit, nan-box variants
@@ -378,10 +384,10 @@ static inline uint32_t mp_clz_mpi(mp_int_t x) {
         || sizeof(mp_int_t) == sizeof(long));
 
     // ugly, but should compile to single intrinsic unless O0 is set
-    if (sizeof(mp_int_t) == sizeof(long)) {
-        return mp_clzl(x);
+    if (mp_check(sizeof(mp_int_t) == sizeof(long))) {
+        return mp_clzl((unsigned long)x);
     } else {
-        return mp_clzll(x);
+        return mp_clzll((unsigned long long)x);
     }
 }