BaseTools/tools_def.template: propagate loss of GCC45 references

BaseTools/tools_def.template: propagate loss of GCC45 references

The last patch decremented references on a number of DEFs. They can be
classified into three groups:

(a) those that remain used by multiple toolchains (refcount >= 2):

- GCC_ASLCC_FLAGS
- GCC_ASLPP_FLAGS
- GCC_HOST_PREFIX
- GCC_IA32_RC_FLAGS
- GCC_PP_FLAGS
- GCC_VFRPP_FLAGS
- GCC_X64_RC_FLAGS
- IASL_FLAGS
- IASL_OUTFLAGS
- UNIX_IASL_BIN

(b) those that are only used by GCC48 (refcount == 1):

- GCC45_ASM_FLAGS
- GCC45_IA32_CC_FLAGS
- GCC45_IA32_DLINK2_FLAGS
- GCC45_IA32_X64_ASLDLINK_FLAGS
- GCC45_IA32_X64_DLINK_FLAGS
- GCC45_X64_CC_FLAGS
- GCC45_X64_DLINK2_FLAGS
- GCC45_X64_DLINK_FLAGS

(c) those that are no longer used (refcount == 0):

- GCC45_IA32_PREFIX
- GCC45_X64_PREFIX

For the members of class (b), expand their definitions at the referring
sites, and remove their definitions.

For the members of class (c), remove their definitions.

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1377
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>