Move some String constructors out of the header

Those do not really need to get inlined and pull std::max which
really wants <algorithm> which is an expensive header.

Author: mawww

src/string.cc

@@ -118,6 +118,21 @@ void String::Data::clear()
     set_empty();
 }
 
+String::String(Codepoint cp, CharCount count)
+{
+    reserve(utf8::codepoint_size(cp) * (int)count);
+    while (count-- > 0)
+        utf8::dump(std::back_inserter(*this), cp);
+}
+
+String::String(Codepoint cp, ColumnCount count)
+{
+    int cp_count = (int)(count / max(codepoint_width(cp), 1_col));
+    reserve(utf8::codepoint_size(cp) * cp_count);
+    while (cp_count-- > 0)
+        utf8::dump(std::back_inserter(*this), cp);
+}
+
 void String::resize(ByteCount size, char c)
 {
     const size_t target_size = (size_t)size;

src/string.hh

@@ -109,21 +109,9 @@ public:
     String() {}
     String(const char* content) : m_data(content, (size_t)strlen(content)) {}
     String(const char* content, ByteCount len) : m_data(content, (size_t)len) {}
-    explicit String(Codepoint cp, CharCount count = 1)
-    {
-        reserve(utf8::codepoint_size(cp) * (int)count);
-        while (count-- > 0)
-            utf8::dump(std::back_inserter(*this), cp);
-    }
-    explicit String(Codepoint cp, ColumnCount count)
-    {
-        int cp_count = (int)(count / std::max(codepoint_width(cp), 1_col));
-        reserve(utf8::codepoint_size(cp) * cp_count);
-        while (cp_count-- > 0)
-            utf8::dump(std::back_inserter(*this), cp);
-    }
     String(const char* begin, const char* end) : m_data(begin, end-begin) {}
-
+    explicit String(Codepoint cp, CharCount count = 1);
+    explicit String(Codepoint cp, ColumnCount count);
     explicit String(StringView str);
 
     struct NoCopy{};