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

jerry-core/CMakeLists.txt

@@ -410,9 +410,9 @@ if(ENABLE_LTO)
   set(JERRY_CORE_PKGCONFIG_CFLAGS "${JERRY_CORE_PKGCONFIG_CFLAGS} -flto")
 endif()
 
-if(JERRY_LIBM)
-  target_link_libraries(${JERRY_CORE_NAME} jerry-libm)
-  set(JERRY_CORE_PKGCONFIG_REQUIRES libjerry-libm)
+if(JERRY_MATH)
+  target_link_libraries(${JERRY_CORE_NAME} jerry-math)
+  set(JERRY_CORE_PKGCONFIG_REQUIRES libjerry-math)
 endif()
 
 separate_arguments(EXTERNAL_LINK_LIBS)