Fixed Clang unknown-warning-ignored warning by ignoring it..... we are truly living in a special time (#1090)

imgui.cpp

@@ -641,6 +641,7 @@
 
 // Clang warnings with -Weverything
 #ifdef __clang__
+#pragma clang diagnostic ignored "-Wunknown-pragmas"        // warning : unknown warning group '-Wformat-pedantic *'        // not all warnings are known by all clang versions.. so ignoring warnings triggers new warnings on some configuration. great!
 #pragma clang diagnostic ignored "-Wold-style-cast"         // warning : use of old-style cast                              // yes, they are more terse.
 #pragma clang diagnostic ignored "-Wfloat-equal"            // warning : comparing floating point with == or != is unsafe   // storing and comparing against same constants (typically 0.0f) is ok.
 #pragma clang diagnostic ignored "-Wformat-nonliteral"      // warning : format string is not a string literal              // passing non-literal to vsnformat(). yes, user passing incorrect format strings can crash the code.