[OpenMP][OMPIRBuilder] Add generation of SIMD align assumptions to OMPIRBuilder

Currently generation of align assumptions for OpenMP simd construct is done
outside OMPIRBuilder for C code and it is not supported for Fortran.

According to OpenMP 5.0 standard (2.9.3) only pointers and arrays can be
aligned for C code.

If given aligned variable is pointer, then Clang generates the following set
of the LLVM IR isntructions to support simd align clause:

; memory allocation for pointer address:
%A.addr = alloca ptr, align 8
; some LLVM IR code
; Alignment instructions (alignment is equal to 32):
%0 = load ptr, ptr %A.addr, align 8
call void @llvm.assume(i1 true) [ "align"(ptr %0, i64 32) ]

If given aligned variable is array, then Clang generates the following set
of the LLVM IR isntructions to support simd align clause:

; memory allocation for array:
%B = alloca [10 x i32], align 16
; some LLVM IR code
; Alignment instructions (alignment is equal to 32):
%arraydecay = getelementptr inbounds [10 x i32], ptr...