<termios.h>: add two new POSIX functions.

musl already added tcgetwinsize() and tcsetwinsize(), but I didn't
notice.

Trivial single-line inlines added to a header that's already written
that way.

Test: treehugger
Change-Id: Iac95ea6a89f3872025c512f7e61987b81d0aafa7
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index e90618d..b3ef185 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -1591,6 +1591,8 @@
     mktime_z;
     __riscv_flush_icache; # riscv64
     __riscv_hwprobe; # riscv64
+    tcgetwinsize;
+    tcsetwinsize;
     timespec_getres;
     tzalloc;
     tzfree;