unit1612: fixed the inclusion and compilation of the HMAC unit test

Follow up to 3f74e5e6 to fix:

- A typo in Makefile.inc where unit1611 was used instead
- Some compilation issues in unit1612.c

Closes #5024

tests/unit/Makefile.inc

@@ -126,7 +126,7 @@ unit1610_CPPFLAGS = $(AM_CPPFLAGS)
 unit1611_SOURCES = unit1611.c $(UNITFILES)
 unit1611_CPPFLAGS = $(AM_CPPFLAGS)
 
-unit1612_SOURCES = unit1611.c $(UNITFILES)
+unit1612_SOURCES = unit1612.c $(UNITFILES)
 unit1612_CPPFLAGS = $(AM_CPPFLAGS)
 
 unit1620_SOURCES = unit1620.c $(UNITFILES)

tests/unit/unit1612.c

@@ -22,6 +22,7 @@
 #include "curlcheck.h"
 
 #include "curl_hmac.h"
+#include "curl_md5.h"
 
 static CURLcode unit_setup(void)
 {
@@ -44,7 +45,7 @@ UNITTEST_START
 
   Curl_hmacit(Curl_HMAC_MD5,
               (const unsigned char *) password, strlen(password),
-              (const unsigned char *) string1, strlen(string1)
+              (const unsigned char *) string1, strlen(string1),
               output);
 
   verify_memory(testp,