Fix a few clang warnings (which -Werror treats as errors)

src/conversions.h

Index: src/conversions.h
diff --git a/src/conversions.h b/src/conversions.h
index 7b02c47f6a0feeec3e960ebc29967274e58eb14d..0f8d5da8ee67568a828820321e6e5a403c00c6c4 100644
--- a/src/conversions.h
+++ b/src/conversions.h
@@ -45,14 +45,14 @@ namespace internal {
 const int kMaxSignificantDigits = 772;
 
 
-static bool isDigit(int x, int radix) {
+static inline bool isDigit(int x, int radix) {
   return (x >= '0' && x <= '9' && x < '0' + radix)
       || (radix > 10 && x >= 'a' && x < 'a' + radix - 10)
       || (radix > 10 && x >= 'A' && x < 'A' + radix - 10);
 }
 
 
-static double SignedZero(bool negative) {
+static inline double SignedZero(bool negative) {
   return negative ? -0.0 : 0.0;
 }