Replace malloc with calloc

- platform layer currently broken (not adapted yet)
- memmory_buffer_alloc too
diff --git a/tests/suites/helpers.function b/tests/suites/helpers.function
index 6977cfa..b9f01ad 100644
--- a/tests/suites/helpers.function
+++ b/tests/suites/helpers.function
@@ -4,7 +4,7 @@
 #include <stdio.h>
 #define mbedtls_printf     printf
 #define mbedtls_fprintf    fprintf
-#define mbedtls_malloc     malloc
+#define mbedtls_calloc    calloc
 #define mbedtls_free       free
 #define mbedtls_exit       exit
 #define mbedtls_fprintf    fprintf
@@ -123,7 +123,7 @@
     void *p;
     size_t actual_len = ( len != 0 ) ? len : 1;
 
-    p = mbedtls_malloc( actual_len );
+    p = mbedtls_calloc( 1, actual_len );
     assert( p != NULL );
 
     memset( p, 0x00, actual_len );
@@ -150,7 +150,7 @@
     if( *olen == 0 )
         return( zero_alloc( *olen ) );
 
-    obuf = mbedtls_malloc( *olen );
+    obuf = mbedtls_calloc( 1, *olen );
     assert( obuf != NULL );
 
     (void) unhexify( obuf, ibuf );
diff --git a/tests/suites/main_test.function b/tests/suites/main_test.function
index c4ce580..ecd5182 100644
--- a/tests/suites/main_test.function
+++ b/tests/suites/main_test.function
@@ -6,7 +6,7 @@
 #include <stdio.h>
 #define mbedtls_exit       exit
 #define mbedtls_free       free
-#define mbedtls_malloc     malloc
+#define mbedtls_calloc    calloc
 #define mbedtls_fprintf    fprintf
 #define mbedtls_printf     printf
 #endif
diff --git a/tests/suites/test_suite_pem.function b/tests/suites/test_suite_pem.function
index 303e4fc..6a62bfe 100644
--- a/tests/suites/test_suite_pem.function
+++ b/tests/suites/test_suite_pem.function
@@ -23,7 +23,7 @@
     ret = mbedtls_pem_write_buffer( start, end, buf, buf_len, NULL, 0, &olen );
     TEST_ASSERT( ret == MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL );
 
-    check_buf = (unsigned char *) mbedtls_malloc( olen );
+    check_buf = (unsigned char *) mbedtls_calloc( 1, olen );
     TEST_ASSERT( check_buf != NULL );
 
     memset( check_buf, 0, olen );