Rename jerry-libm to jerry-math (#4410)

That "libm" in the name of the library resulted in awkward naming
on *nix systems (`libjerry-libm.*`, "lib" occurring twice). And the
name of the corresponding header is `math.h` anyway.

Note that this is a breaking change in some sense. The commit
contains no API change, but the build system does change for users
of the math library.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

tools/check-license.py

@@ -42,7 +42,7 @@ INCLUDE_DIRS = [
     'cmake',
     'jerry-core',
     'jerry-ext',
-    'jerry-libm',
+    'jerry-math',
     'jerry-main',
     'jerry-port',
     'targets',