Makefile.vc: add DLL configs

(release|debug)-dynamic
These configurations will produce a dll in bin/ and an import lib under
lib/.
Currently the -noasm switch in the examples will be disabled for these
builds due to a dependency on VP8EncGetCPUInfo.

Change-Id: I2cbac0064f0e500698d14ffc03200791ca837090
diff --git a/examples/cwebp.c b/examples/cwebp.c
index bc29880..0665cc0 100644
--- a/examples/cwebp.c
+++ b/examples/cwebp.c
@@ -53,7 +53,9 @@
 
 #include "webp/encode.h"
 #include "stopwatch.h"
+#ifndef WEBP_DLL
 extern void* VP8EncGetCPUInfo;   // opaque forward declaration.
+#endif
 
 //-----------------------------------------------------------------------------
 
@@ -689,7 +691,9 @@
   printf("  -short ................. condense printed message\n");
   printf("  -quiet ................. don't print anything.\n");
   printf("  -version ............... print version number and exit.\n");
+#ifndef WEBP_DLL
   printf("  -noasm ................. disable all assembly optimizations.\n");
+#endif
   printf("  -v ..................... verbose, e.g. print encoding/decoding "
          "times\n");
   printf("\n");
@@ -808,8 +812,10 @@
     } else if (!strcmp(argv[c], "-resize") && c < argc - 2) {
       resize_w = strtol(argv[++c], NULL, 0);
       resize_h = strtol(argv[++c], NULL, 0);
+#ifndef WEBP_DLL
     } else if (!strcmp(argv[c], "-noasm")) {
       VP8EncGetCPUInfo = NULL;
+#endif
     } else if (!strcmp(argv[c], "-version")) {
       const int version = WebPGetEncoderVersion();
       printf("%d.%d.%d\n",