Various coverage improvements.

Mostly from extra test cases, but also:

* Move the fgets size < 0 assertion into fgets.

* Use ELF aliases for strtoq/strtouq rather than duplicating code.

* Don't check uname() succeeded, since it can't fail.

Test: treehugger
Change-Id: I2e6b3b88b0a3eb16bd68be68b9bc9f40d8043291
diff --git a/tests/sched_test.cpp b/tests/sched_test.cpp
index 9309a7f..03e8062 100644
--- a/tests/sched_test.cpp
+++ b/tests/sched_test.cpp
@@ -301,3 +301,7 @@
   // don't behave as POSIX specifies. http://b/26203902.
   ASSERT_EQ(0, sched_setscheduler(getpid(), original_policy, &p));
 }
+
+TEST(sched, sched_getaffinity_failure) {
+  ASSERT_EQ(-1, sched_getaffinity(getpid(), 0, nullptr));
+}