give importers the headers module templates need

A template defined in a module interface is instantiated in the importing
unit, where its body's types must be complete. A declaration reaching the
importer only through the interface's global module fragment is not
enough for MSVC: cParser::operator>> uses std::stringstream, and every
unit that parsed a float got an incomplete type.

526 headers across 161 units, derived from what each interface's template
bodies actually name.

application/application.cpp

@@ -1,4 +1,10 @@
 module;
+#include <deque>
+#include <limits>
+#include <mutex>
+#include <ostream>
+#include <type_traits>
+#include <unordered_map>
 #include <cstring>
 #include <cstdint>
 #include <array>