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/unit-tests/Makefile

@@ -15,7 +15,7 @@
 CC=gcc
 LDFLAGS=-lm
 
-GENS=gen-test-libm
+GENS=gen-test-math
 
 .PHONY: build
 build: $(GENS)
@@ -24,5 +24,5 @@ build: $(GENS)
 clean:
 	rm -f $(GENS)
 
-gen-test-libm: gen-test-libm.c
+gen-test-math: gen-test-math.c
 	$(CC) $< -o $@ $(LDFLAGS)