Since commit 38aab379 (Set CMAKE_<lang>_COMPILER_ID for VS generators,
2011-09-02) the VS IDE generators set the C and C++ compiler id to MSVC
and the Fortran compiler id to Intel.  This caused the Fortran test to
fail compatible compiler detection because the if() test

  "${CMAKE_C_COMPILER_ID}" MATCHES "MSVC"

is evaluated as the "var MATCHES regex" signature which evaluates the
compiler id "MSVC" as a variable which is defined to 1 which does not
match "MSVC".

Combine tests for non-identical but compatible compiler vendors into a
single regex match whose left hand side will not be defined as a
variable.