Unit testing in CI (#651)

- in appveyor, install clang and cmake in cygwin, enable package upgrades, and build cmocka and enable testing for gcc only
- in `gitignore`, ignore generated cmocka folder
- in travis, use brew in osx to install cmocka, and enable testing for gcc and clang on os x and linux
- in `Makefile`, change to use `uname -s` to determine os type
- make `install-cmocka-linux.sh`, a simple shell script to download and install cmocka on linux
- in `bindings/Makefile`, enable `make -c` to call subdirectory makefiles instead of `cd [dir] && make` and include environment variables for runtime access to generated libraries
- in `samples/Makefile`, change to use `uname -s` to determine os type, remove `clean_bins` from `all` command, and include `Werror` for compile strictness
- in `tests/unit/Makefile`, add `cflags` for compile time access to cmocka headers and library, include execute vars for runtime access to cmocka and unicorn libs
- in `tests/unit/test_tb_x86.c`, comment out assert that would not compile

tests/unit/test_tb_x86.c

@@ -222,7 +222,7 @@ static void test_tb_x86_64_32_imul_Gv_Ev_Ib(void **state)
 {
     uc_engine *uc = *state;
     uc_hook trace1, trace2;
-    void *mem;
+    //void *mem;
 #ifdef RIP_NEXT_TO_THE_SELFMODIFY_OPCODE
     // These values assumes just before PC = 0x60000021
     int64_t eax = 0x00000041;
@@ -245,8 +245,9 @@ static void test_tb_x86_64_32_imul_Gv_Ev_Ib(void **state)
     int64_t edi = 0x488ac239;
 #endif
 
-    mem = calloc(1, CODE_SPACE);
-    assert_int_not_equal(0, mem);
+    //mem = calloc(1, CODE_SPACE);
+    // TODO examine
+    //assert_int_not_equal(0, mem);
 
     uc_assert_success(uc_open(UC_ARCH_X86, 
                               UC_MODE_32,