Change 'mem' namspace to 'jmem'

The 'mem_' prefix is too general, so it might clash with
symbols in other libraries. Renamed the directory, file,
funtion and type names.

Related issue: #1052

JerryScript-DCO-1.0-Signed-off-by: László Langó llango.u-szeged@partner.samsung.com

tests/unit/test-strings.c

@@ -107,7 +107,7 @@ main (int __attr_unused___ argc,
 {
   TEST_INIT ();
 
-  mem_init ();
+  jmem_init ();
   lit_init ();
   ecma_init ();
 
@@ -221,7 +221,7 @@ main (int __attr_unused___ argc,
 
   ecma_finalize ();
   lit_finalize ();
-  mem_finalize (true);
+  jmem_finalize (true);
 
   return 0;
 } /* main */