Reprioritize gcc over clang.

We got a number of complaints with the recent move to prioritize clang
over gcc.  The biggest one was the lack of good OpenMP support in
clang.

http://clang-developers.42468.n3.nabble.com/RFC-OpenMP-Support-in-Clang-td4029194.html

confdb/aclocal_cc.m4

@@ -11,7 +11,7 @@ AC_DEFUN([PAC_PROG_CC],[
         dnl developers notice this case.
         AC_BEFORE([$0],[AC_PROG_CC])
 	PAC_PUSH_FLAG([CFLAGS])
-	AC_PROG_CC([icc pgcc xlc xlC pathcc clang gcc cc])
+	AC_PROG_CC([icc pgcc xlc xlC pathcc gcc clang cc])
 	PAC_POP_FLAG([CFLAGS])
 ])
 dnl

confdb/aclocal_cxx.m4

 dnl PAC_CXX_SEARCH_LIST - expands to a whitespace separated list of C++
 dnl compilers for use with AC_PROG_CXX that is more suitable for HPC software
 dnl packages
-AC_DEFUN([PAC_CXX_SEARCH_LIST],[$CCC icpc pgCC xlC pathCC clang++ g++ c++ cc++ cxx CC cl])
+AC_DEFUN([PAC_CXX_SEARCH_LIST],[$CCC icpc pgCC xlC pathCC g++ clang++ c++ cc++ cxx CC cl])
 dnl PAC_PROG_CXX - reprioritize the C++ compiler search order
 dnl NOTE: this macro suffers from a basically intractable "expanded before it
 dnl was required" problem when libtool is also used