base: avoid use of deprecated base/printf.h

Besides adapting the components to the use of base/log.h, the patch
cleans up a few base headers, i.e., it removes unused includes from
root/component.h, specifically base/heap.h and
ram_session/ram_session.h. Hence, components that relied on the implicit
inclusion of those headers have to manually include those headers now.

While adjusting the log messages, I repeatedly stumbled over the problem
that printing char * arguments is ambiguous. It is unclear whether to
print the argument as pointer or null-terminated string. To overcome
this problem, the patch introduces a new type 'Cstring' that allows the
caller to express that the argument should be handled as null-terminated
string. As a nice side effect, with this type in place, the optional len
argument of the 'String' class could be removed. Instead of supplying a
pair of (char const *, size_t), the constructor accepts a 'Cstring'.
This, in turn, clears the way let the 'String' constructor use the new
output mechanism to assemble a string from multiple arguments (and
thereby getting rid of snprintf within Genode in the near future).

To enforce the explicit resolution of the char * ambiguity, the 'char *'
overload of the 'print' function is marked as deleted.

Issue #1987

repos/gems/src/lib/file/file.cc

@@ -12,7 +12,7 @@
  */
 
 /* Genode includes */
-#include <base/printf.h>
+#include <base/log.h>
 
 /* gems includes */
 #include <gems/file.h>
@@ -42,7 +42,7 @@ File::File(char const *name, Genode::Allocator &alloc)
 {
 	int const fd = open(name, O_RDONLY);
 	if (read(fd, _data, _file_size) < 0) {
-		PERR("reading from file \"%s\" failed (error %d)", name, errno);
+		Genode::error("reading from file \"", name, "\" failed (error ", errno, ")");
 		throw Reading_failed();
 	}
 	close(fd);