acpihelp: Replace c Lib APIs with new APIs to improve portability

1.Replaced printf with AcpiOsPrintf to make it linkable under EFI shell.
2.Replaced the string APIs with new string API wrappers so that these string APIs
can be used under EFI shell. (Replaced strXXX with ACPI_STRXXX, ACPI_STRXXX is wrapper of
AcpiUtStrXXX)

Tested under unix environment using "make acpihelp SHARED=false" and no regressions were found.

Signed-off-by: Yizhe Wang <yizhe.wang@intel.com>
acpihelp: added environment macro

Added the macro "USE_NATIVE_ALLOCATE_ZEROED" for acpihelp to fix the bug:
"Undefined reference to 'AcpiOsAllocateZeroed'"

Signed-off-by: Yizhe Wang <yizhe.wang@intel.com>
acpihelp: implemented new APIs to improve portability

1.Implemented AcpiUtStrpbrk as a wrapper of strpbrk.
2.Implemented AcpiUtStrtok as a wrapper of strtok.

Tested the two functions in unix and no bugs are found.

Signed-off-by: Yizhe Wang <yizhe.wang@intel.com>
acpihelp: added build support

Added the following changes so that users can build executables for EFI shell:
1.Added a Makefile for acpihelp.
2.Modified Makefile.config.

To build, use "make OS=efi acpihelp".

Signed-off-by: Yizhe Wang <yizhe.wang@intel.com>