Fix PCRE build under non-__GNUC__ compilers

Fix PCRE build under non-__GNUC__ compilers

PCRE's JIT has several paths that end in a #error under compilers that
don't #define __GNUC__.

This is because either
- those platforms were unavailable to PCRE devs so they were not tested;
- the #ifdef guards inline assembly fragments in GCC (AT&T) syntax;
- the #ifdef guards functions present f.i. in ARM's EABI and unavailable
  f.i. under WinCE.

This commit disables PCRE's JIT under ARM and MIPS unless __GCC__ is
defined. The MIPS #define from MSVC (_M_MRX000) is also dropped.

Change-Id: I59f959c321413845ffbdf1ac32740b400422e0ee
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Björn Breitmeyer <bjoern.breitmeyer@kdab.com>
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Andreas Holzammer <andreas.holzammer@kdab.com>