Fix linkage errors when linking with a shared library (#2011)

src/format.cc

@@ -24,9 +24,9 @@ int format_float(char* buf, std::size_t size, const char* format, int precision,
                        : snprintf_ptr(buf, size, format, precision, value);
 }
 
-template dragonbox::decimal_fp<float> dragonbox::to_decimal(float x)
+template FMT_API dragonbox::decimal_fp<float> dragonbox::to_decimal(float x)
     FMT_NOEXCEPT;
-template dragonbox::decimal_fp<double> dragonbox::to_decimal(double x)
+template FMT_API dragonbox::decimal_fp<double> dragonbox::to_decimal(double x)
     FMT_NOEXCEPT;
 
 // DEPRECATED! This function exists for ABI compatibility.

src/os.cc

@@ -315,7 +315,7 @@ long getpagesize() {
 #  endif
 }
 
-void ostream::grow(size_t) {
+FMT_API void ostream::grow(size_t) {
   if (this->size() == this->capacity()) flush();
 }
 #endif  // FMT_USE_FCNTL