Error out on invalid empty prototypes

This way, a function prototype like `glms_mat3_identity()` will not
compile, instead you have to change it to the proper
`glms_mat3_identity(void)`.

Makefile.am

@@ -12,7 +12,8 @@ AM_CFLAGS = -Wall \
             -O3 \
             -Wstrict-aliasing=2 \
             -fstrict-aliasing \
-            -pedantic
+            -pedantic \
+            -Werror=strict-prototypes
 
 lib_LTLIBRARIES = libcglm.la
 libcglm_la_LDFLAGS = -no-undefined -version-info 0:1:0