patch 8.1.0785: depending on the configuration some functions are unused

Problem:    Depending on the configuration some functions are unused.
Solution:   Add more #ifdefs, remove unused functions. (Dominique Pelle,
            closes #3822)
diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index 72d28c5..9fe22a3 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -1578,7 +1578,7 @@
 #  endif
 # endif
 
-#if defined(FEAT_SYN_HL) && defined(FEAT_RELTIME) && defined(FEAT_FLOAT)
+#if defined(FEAT_SYN_HL) && defined(FEAT_RELTIME) && defined(FEAT_FLOAT) && defined(FEAT_PROFILE)
 # if defined(HAVE_MATH_H)
 #  include <math.h>
 # endif