CheckTypeSize: Unset variables used during parsing when no longer needed

When the macro is invoked several time, the parsing variables are not
unset and therefore used for all the following calls.

This fixes issue #14690
FindJNI: Set JAVA_INCLUDE_PATH2 for darwin (#14508)
Merge topic 'find-java-os-x-fixes' into next

519084c FindJNI: Set JAVA_INCLUDE_PATH2 for darwin (#14508)
Merge topic 'CheckTypeSize_fix_multiple_invocation' into next

37136b3 CheckTypeSize: Unset variables used during parsing when no longer needed