Remove unsupported xlc16 compile options on aix

When compiling jdk/jdk on AIX (using current xlc16 / xlclang) we run into these warnings :

warning: 1540-5200 The option "langlvl=c99vla" is not supported. :
This option controls variable length arrays / Enables or disables support for C99-type variable length arrays.
warning: 1540-5200 The option "langlvl=noredefmac" is not supported. :
Controls whether a macro can be redefined without a prior #undef or undefine() statement.

see https://www.ibm.com/support/knowledgecenter/SSGH3R_16.1.0/com.ibm.compilers.aix.doc/compiler.pdf


The mentioned options are only available with the legacy xlc (non xlclang).
I propose to remove these options, because xlc16 / xlclang is now the default compiler.